More ideas for the PILE:
Shadow Doors/Ghost Doors.
A incorporeal transluscent door type that doesn't have collision. (Basically being walkthrough if you don't meet the condition and dissapearing after the keys are spent. This could be paired with any other door type, and could lead to intresting dynamics.
Edit: holy crap I predicted the name. dang. Well this is now unoriginal. Big sad :(
Skeleton Keys.
A master-esque key that turns the door it touches into a ghost door. Negative versions turn a door back.
Badges.
Gold, pure, and skeleton stickers that are placed on doors, functioning as a immunity to those door types. Essentially a extra outside color without the cost swap.
Minilocks.
These would be doors that effectively would function as keys, being put in a 1-10 door inventory when picked up. They could be stacked and would jam you from using master keys, because they would automatically trigger when their conditions are met, being resolved from top to bottom, left to right. I hope you aren't carrying any brown keys.
Quantum Doors.
Doors with a dotted gray line between them. When one of them disappears or is cloned, the other is as well. Effectively being a minor Linked Door. When one is salvaged, both of them appear in the same spot they were relative to each other. A Quantum Door would also count as one door for the purpose of all auras.