Okay, but what if we keep going? What about Part 2?
The Vast Depths
The Great Beyond's counterpart. In the entrance area, the ground is more red and pink than the original orange and yellow, the sky is darker, the trees are black and leafless, and red streaks fly up instead of down. You're headed very deep into this world...
Salvage Points variation:
Preservation Points
Preservation Points look similar to Salvage Points, but with an icon of a key inside them instead of arrows. Instead of an ID number, Preservation Points have a color. When you touch a Preservation Point, the next time you enter a level or win a level, whatever your Key count of that color was, that count carries over into the level you just entered/returned to. (The Preservation Point deactivates after being used). For example, if you have 28 Pink Keys, touch a Pink Preservation Point, spend 6 Pink Keys, and enter a level, you'll start that level with 22 Pink Keys, because that's how many you had when you entered it. Likewise, if you have 3 Purple Keys, touch a Purple Preservation Point, and then win the level, you'll have 3 Purple Keys on the world map you returned to. Preservation Points are automatically deactivated if you exit a level, though - if you want to preserve a Key count from a level onto the world map it came from, you have to win that level! Unlike Salvage Points, touching a Preservation Point when you already have one active does not deactivate the first one, so it's possible to carry over multiple Key counts into a single level. Warping with the Warp Rod deactivates all currently active Preservation Points, so you can't preserve Key counts through a warp - you need to rely on the entrances that are actually available.
Yes, Glitch Preservation Points change color like other Glitch objects do, so the color they preserve is dependent on what the most recent Spend Color was when a level change occurs. You definitely can't use Master Keys on Preservation Points, though, and you can't curse a Preservation Point - just because these things have color doesn't mean they act like doors. As for Stone Keys, when they're Preserved, the earned count is added to the Preserved count: for example, if you've currently earned 14 Stone Keys and then preserve 30 Stone Keys, you'll have 44 Stone Keys upon the level transition.
Like The Great Beyond, The Vast Depths is split into chapters, each of which explores Preservation Points in increasing complexity. The Great Beyond's chapters are apparently based on the four seasons, so I'll base the Vast Depths chapters on the four classical elements.
Chapter V1 is Flaming Forest: a forest fire has spread into the Autumn Woods, setting the trees alight in blazing red flame. Sparks and ashes float up into the wind created by the fire. This chapter, as the first Preservation Points chapter, sticks to having Preservation Points within the levels, so you have to win the levels with the right Key counts so you can take those Keys onto the world map and open the doors there.
Chapter V2 is Subterranean Palace: the Frozen Palace has sunken deep underground. Its ice has turned to dirt and stone, and boulders, chunks of ore, and ant tunnels are scattered throughout the walls. This chapter introduces Preservation Points on the world map, so now you have to solve parts of the world map puzzle to bring in the right amount of Keys of the right colors into the levels.
Chapter V3 is Clouded Castle: the Sunshade Castle has risen into the clouds, taking on a more white and blue color scheme, with the ground being made of clouds and wind rushing by in the background. Now entrances to levels start showing up within levels themselves, so you can preserve Key counts from one level into another level, or even into itself!
Chapter V4 is Labyrinth of the Lake: the Dream Labyrinth has been altered to have an "aquatic palace" feel, with waterfalls flowing along the walls, and an underwater background with coral reefs. As with T4, this chapter throws together all of the ways to use Preservation Points from the previous chapters into an advanced, winding, multi-layered (and, given entries within levels themselves, perhaps even recursive) puzzle process.
There's also a Chapter V5: Essential Cosmos, which is based on the fifth element, "quintessence". The background here is black, with twinkling points like stars in the night sky, wisps of various shades of blue, purple, and pink passing through the background, pentagons of various greys (with perhaps some slight color to them) rotating in the background, and a big dodecahedron spinning in the background similar to the rotating cube in Focal Point - the aesthetic of this world is sort of a mix between outer space and Focal Point (with a hint of The Cool Place), but with pentagons instead of squares. Salvages, which have been absent throughout the return worlds, show up here again, and after a few levels that just use Salvages with the new mechanics from the Return Worlds, you reach levels that have both Salvages and Preservation in the mix! The Salvage IDs here are 100 and higher, too high for the Omega Terminal to access, so you're not recoloring these ones.
There's a single color that every Vast Depths chapter has had a Preservation Point of, and only at the end of Essential Cosmos can you get a tessarine amount (i.e. an amount including h) of that Key color. The beginning of the Vast Depths has a Door of that color with h in its cost tucked away, and so you have to get there by retracing back through the Vast Depths, activating the Preservation Point of that color in each chapter in backwards order until you reach the beginning of the Depths to open that door. What's behind that door? World R0, of course!
World 0 doesn't introduce any new mechanics, but I still have an idea for World R0: The Cool Museum, a mix of World 0 and the Lockpick Museum. The ground tiles are the dark blue of the Lockpick Museum background, but the background is a light blue, and the rectangles of World 0 are still passing by in the background (or maybe they're some other shape instead, like pentagons or hexagons). This world's levels each use some complicated contraption to simulate a mechanic that, whether from the Lockpick Museum or from fanmade suggestions, is not in the game, and create a puzzle using that mechanic's emulation.
There are several places things could go from here. If we just want to do Omega Keys again, then there's two ways it could go: the most obvious way is to have the reward for beating R0 be an extension to the Omega Terminal that lets it access the Salvage IDs used in the Vast Depths, and have more Omega Key puzzles to obtain the Checkerboard (and/or Transparent, depending on which one(s) is/are included in R2), Ice, Mud, Ink, Crimson, Forest, Navy, Rainbow, Stained Glass, and Alarm Omega Keys (plus Omega Keys for each level of Laggy Glitch), but it could also go by a different progression: you gain access to all of those Omega Key colors upon beating R0, but now you have to go collect "Numbered Omega Keys", which, instead of unlocking new colors for the Terminal, unlock new Salvage IDs for the Terminal.
However, I have an idea for something different. Omega Keys serve two roles in Lockpick: they're responsible for meta puzzle craziness, and then later on they're used for Chapter EX puzzles. I've thought of a different idea to replace them for each of these two roles, and here's the first one.
Omega Keys, as meta-puzzle goals, variation:
Diamond Keys
Diamond is a Key color with a special trait: changes to Diamond objects are forever. When you collect a Diamond Key, you keep it, even when switching between levels. Likewise, any door with Diamond on it remains destroyed even when switching between levels - if a door changes your Diamond Key count, that Diamond Key count change is also retained, but changes to other Key counts reset as usual (unless Preserved, of course). In other words, your Diamond Key count is always preserved, and Diamond Key pickups and Diamond doors are destroyed permanently... but you can still undo, of course. If you re-enter a level, where all the rest of the actions you did that level are undone but the Diamond actions remain, you can still use Undo to undo the Diamond Key count changes and Diamond door destructions that level caused. For ease of implementation, you can only undo individual actions while they're part of the normal undo chain - once you've left and re-entered a level, if you want to undo its Diamond actions from previous visits, you have to undo all of that level's Diamond actions at once. World R0 would have an entrance to the "Crystal Lab", which has a terminal in it that lets you view all changes to your Diamond Key count, where they came from, and what Diamond doors have been destroyed, and lets you Diamond-undo individual levels from the terminal.
The Diamond terminal would, similar to the Omega Terminal, let you unlock new worlds with enough Diamond Keys - doing so simply requires you have enough, it doesn't actually spend them. The first thing it unlocks, the equivalent to the revealing of hidden Salvage Points, is revealing hidden entrances (such as an entrance from the Chapter V1 map to, say, Page 3 of Chapter V2), letting you jump around between world maps and levels to pull off some crazy Preservation shenanigans, which you'll need in order to get the rest of the Diamond Keys.
So what do those new worlds do?
World R12 / RR1: Return to Return to Doorhaven
It's time to feel nostalgic for feeling nostalgic for World 1
Infinite Keys variation:
Recurrent Keys and Doors
Similarly to Infinite Keys, any Key type can be Recurrent, signified by a looping arrow next to the Key (in the same location as Infinite Keys' infinity symbol). When you collect a Recurrent 1 Red Key, that Key pickup becomes transparent and no longer solid, so you can pass through it freely, but in addition to gaining the 1 Red Key from picking it up initially, every time you open a door (or a copy of a door), the Recurrent Key triggers again, giving you another 1 Red Key. While a Recurrent Key is active, its looping arrow symbol is glowing. Multiple Recurrent Keys can be active at once. Once a Recurrent Key has been activated, it cannot be de-activated.
There can also be Recurrent Doors (which use the same symbol on the corner of the door): a Recurrent Door also goes transparent and non-solid when opened, and every time another door is opened, its spending cost is re-applied (though, with Blast/All/Glitch locks, that cost may be a different number and/or color than it was last time!). If a Recurrent Door's locks are no longer satisfied when it tries to trigger, it fails to apply its spend cost again and it disappears. If a Recurrent Door has multiple copies, it does not become non-solid while it has any copies remaining (I imagine that its exterior remains opaque but its locks become transparent to indicate you can't open them at the moment, and of course the looping arrow is glowing), but it's still activated and performs Recurrent triggers until its locks fail, at which point it reforms and you can open another of its copies. While a Recurrent Door is active, you can't interact with it: you can't open it again, you can't use a Master Key on it, you can't curse it, and so on. If it still had copies left, then it essentially acts like a plain wall until the recurrence ends and it can be opened again.
When order matters (such as when Recurrent Keys of non-regular types, like Signflip or Star Keys, get involved, or when Recurrent Doors are involved... like at all), keep in mind that Recurrent Keys and Doors trigger in the order they were activated. The Glitch color(s) change before Recurrent Keys and Doors trigger, and they do change again after each Recurrent Door opening. Using a Master Key on a Recurrent Door does not activate its recurrence, and using a Master Key does not count as "opening a door" for the purposes of triggering Recurring objects. For the purpose of Salvaging, a Recurrent Door only counts as destroyed when it's fully destroyed, i.e. when a failure to meet its requirements causes its recurrence to stop and makes it disappear. A Key cannot be both Recurrent and Infinite.
Gates variation:
Solidside Gates
What if each side of a Gate could operate separately? This is an idea for expanding Gates' functionality: now, each of the four edges of the Gate can be one of four types: "always closed", "always open", "normal behavior" (closed if you don't meet the requirements, open if you do), or "inverse behavior" (open if you don't meet the requirements, closed if you do). This means, for example, you can have a Gate where only the bottom edge is open if you don't satisfy the Gates' locks, the left and right edges are open if you do satisfy the Gates' locks (but the bottom edge is now closed), and the top edge is always closed. A closed edge of a Gate is solid from the outside, but while you're inside a Gate, the whole thing is non-solid, so the edge rules only restrict what side(s) you can enter the Gate from, not the sides you can exit it from.
To represent this, if a Gate has any non-normal edges, thin lines are drawn on the edges of the Gate: a red line for an always closed edge, a green line for an always open edge, a blue line for an inverse behavior edge, and a black line for a normal behavior edge. These lines are opaque if the edge is closed, semi-transparent if the edge is open. The Gate itself, i.e. the part other than the edge, is always opaque when you don't meet its requirements, semi-transparent if you do meet its requirements. If you're inside the Gate, the Gate and all its edges become semi-transparent.
Chapter VE: Sunset Garden
As your time in the Vast Depths is setting, so too is the sun on the Garden of Dreams. The grass is more yellow-y than before, and instead of a rainbow in the background, there's a sunset with a brilliant gradient of color.
Omega Keys, as Salvage Recoloring, variation:
Epsilon Keys
Epsilon is a key "color" (I imagine them as a dark chartreuse or dark sea green color; perhaps a gradient of greens between the two) with a special property that lets Epsilon Keys behave like Omega Keys, but instead of changing the colors of locks, they change the numbers of locks. Each level in Sunset Garden has an "Epsilon Terminal", which can access some of the doors within that level (perhaps all of them in some levels, but in some levels there are doors and/or individual locks you can't access from the Epsilon Terminal). At an Epsilon Terminal, you can spend 1 Epsilon Key to increase the number on any lock accessible at that Terminal by 1. Likewise, -1 Epsilon Keys can be spent to decrease a lock's number by 1, and same goes for i, -i, j, -j, h, and -h. Once you spend an Epsilon Key at an Epsilon Terminal, you can't retrieve it without undo/restart, but Epsilon Keys are not permanent like Omega Keys are, they and their changes reset after the level like other key colors do. Epsilon is a perfectly valid color for doors and locks.
The Epsilon Terminal will not change whether a lock is Regular or Exact, but it can change the numbers on both types. Locks made to have a count of exactly 0 by the Epsilon Terminal become neither positive nor negative, so they can be opened regardless of your Key count of that color. The Epsilon Terminal still doesn't allow single locks with multiple dimensions of cost, so to turn a 4 Green lock into something involving i, you'll need to get rid of that 4 first. The Epsilon Terminal cannot affect Blank, Blast, or All locks.
The alternative to Bridge to New Memories is "Crystal Culmination", a set of a few levels interconnected with entrances, where Diamond Keys are used to their fullest extent, so despite being multiple levels, it's one big puzzle where some changes carry over across the entire process of solving it. Only the level you start in has a goal in it, but in order to reach it, you need enough Diamond Keys, which you can only get by going through the whole process. Your reward for clearing this puzzle (in addition to, y'know, beating the return worlds as a whole), is the Diamond Omega Key, so once you clear this puzzle you can easily get as many Diamond Keys as you want. (If Omega Keys weren't involved at all in the Vast Depths, then if you didn't get them already, you'd also get the rest of the Omega Keys of the Return World colors here, so you can go mess around with them in the Great Beyond levels)
As for World Omega... World RΩ would probably just be more of the same kinds of puzzles as World Ω itself, but now including the mechanics from the return worlds as well. The name I've thought of for this one is "Further Horizons", and it would be a color-inverted version of the original World Ω, i.e. dark grey with magenta tint.