These are some great ideas for the Revisionists. That example for the Inversion Lab is really good, and exactly the type of thing I would love to see players at the table use it for.
The Memory Tomb has a similar format to claims in the Black Hats and Dynasty which also provide a bonus to various functions while the players are taking action on their "home turf." It's up to you and the table to negotiate the exact prerequisites to get those bonuses, as they are deliberately written loose. Really the primary goal was to make the player's headquarters feel gradually more personalized and under their control (this is especially true for the Dynasty, which can rack up a lot of bonuses for fighting on home turf). This is important since the Entanglement table in downtime includes a few results that prompt a "home invasion" scenario where the crew's HQ or Claims can come under attack. In the specific example of the Memory Tomb, it might not exactly provided combat bonuses, but it's definitely good for research and information gathering... maybe that's something the crew might desperately need to do while under siege from an enemy? That could be a cool scene.
Message in a Bottle is definitely one of the most challenging special abilities for the reader in HW, but I think you've got the idea. It's deliberately nebulous, but the implication is that one of your crew (perhaps even a crew member not yet created?) is the Mysterious Stranger, from your future (or maybe a bad future, and they're trying to save you from it?). The Revisionists are full of this sort of thing, where the mechanical bonus is here for you to drape your own story over.
Stable Loops is exactly as you say in my imagination. It's a Flashback, except the cost is different because it's a Flashback you have not done yet. The memory cost may be the computational strain on the user of memorizing the scenario, the precise timestamps, and the exact circumstances which need to be altered in the future so they can seamlessly "save themselves" in the past. At the table, you might frame the scene as a kind of Flash-Forward, where the player narrates how an older version of their character goes back in time to help themselves in this present moment... but basically framed in the same way at the table as an ordinary flashback.
In general I knew for my recent update that the themes of HW can be a little esoteric, and so one of the goals was to throw in some actionable prompts for adventure lines and story hooks to help get everyone's imagination stirring. And yeah, the Revisionists are pretty crazy conceptually so they need the help most of all out of my existing crew types.
To that end, the Player Handouts section has score prompts now! These are towards the back of the PDF in the GM handouts area. Here's some examples from the Revisionists page (Black Hats and Dynasty also have their own tables, the Council will get one with my next update).
