Welcome! I'll answer your questions in order, feel free to follow-up with any others!

1. Chaos level is similar to Wanted level from blades in the dark. It's tracked on the Crew sheet, and it usually increased by having the Heat on the crew reach maximum. The idea is that your crew's Heat-increasing actions in World are actively destabilizing the status quo, which has disruptive effects on World's infrastructure and also makes the Administration less lenient with the crew (as they realize that you're the source of the instability!).

It's actually very good feedback to hear that there's a (obvious, in hindsight!) possibility for confusion with the regional rating for Data Structure between stable and chaotic. That's not meant to affect the Chaos level, and I could probably do better by renaming that to clear any confusion. Great question!

2. Yes!  Here's a preview of the Revisionists:

3. The MEM system is designed to give flexibility to the characters. The core system of the game (blades in the dark) was designed to run heists, and heist fiction (especially cinema) is often about the characters showing us their cool equipment right at the moment they need it. In-detail planning often happens off-screen. Another example of this principle at work is the system for Flashbacks, which let you back-fill in clever planning on the part of your characters in the middle of the action.

The way MEM is represented in Hello, World is that until a PC locks in their MEM slot by announcing what they're carrying with the slot, it's quantum: a piece of gear that their character has planned for and knows (or suspects) they'll need later in the score, but since we're discovering how the heist goes as it happens, we the players don't need to plan that stuff out ahead of time. In Hello, World, depending on how you envision the setting, it might actually be quantum data that turns into the item, or information that is downloaded just as needed, but that's up to you!

Those are strong ideas! One thing players also do is just make a new User character, and introduce them as a switch-hitter who fills in temporarily with the crew while their PC is on the stack (this is common in Blades as well, which uses Incarceration as a potential outcome that can also take a PC out of the game for lengthy periods). Depending on how "hard" the GM and players like to play the system, it's possible to chew through PCs! This can be used to tell a generational story about the founding members of the crew and how the torch gets passed as they fade out of the story and get replaced by fresher blood. It's not necessary to play the game that way, you can certainly end a campaign with the same character you started with if you play them a bit more cautiously, but it's one way to do it.

One of my 'stretch goals' is to eventually have playbooks for Shades and Process, which would introduce official options for the other ideas you've mentioned. In the meantime, check out the Daemon if you want to see one example of this!

There's a lot of setting writing I need to do to flesh out the idea of Process in the setting, but it's definitely meant to be something you can adapt to your own ideas... and you definitely have some great ones! I'm glad the setting inspires!

Looking at Authority, now, and trying to get an idea of how it works. Let me know if I missed something.

Let's say my crew is ready to move up to Tier 1. They've made a name for themselves in the local Bohemian society, and decide they want a mobile art studio and base of operations. They can probably Compile one from scratch, or Format an old airship after using Restore to get it functioning, again. We spend 12 Rep, minus any discount we might have for leverage.

Compile:

• Scale 2 (Building-sized: They want it to be fairly spacious.)
• Duration: 6 (A Demi-iteration: They want it to last.)
• Quality 3 (Might as well make it nice.)

The total is 11, plus any points the GM might assign to make it mobile, if slow. The crew pays that in stress, and we go over the factions to see who's attitude would be affected by our new airship.

Alternatively, we might work on obtaining and restoring an existing airship, and then use Format to improve it.

• Scale 2 (Building-sized)
• Quality 3 (Starting from 0, up to 3)
• Force 2-4? (It's a very large vehicle, but no combat functions, aside from possibly ramming.)

In this case, the total would be 7-9, making it less stressful, but it would require more initial work and someone with a strong Restore function. Follow up with the same questions as we increase our Tier.

I'm also thinking about the issue of Scores, and what would constitute them for a not-so-criminal group of bohemians. Some ideas that seem the most appropriate:

• Adding graffiti in a secure area. (Stealth)
• Obtaining Leverage by recruiting or infiltrating (Social)
• Protecting our people on the inside by sowing confusion or allaying suspicion. (Deception)
• Defense? I imagine some "critics" would not take kindly to our crew adding fractal graffiti to their territory. (Assault or Transport)

Writing up some notes for a game of HW I'm hoping to run or play, since I've got some interested players. I'm filling in gaps and homebrewing from the Forged in the Dark SRD. Currently breaking my brain on the Revisionist preview you posted earlier, since I'm excited about that crew type:

1. Inversion Lab: "Retroactively plant items in Archives."

My current interpretation: I have to be able to fit a "host object" into the lab. For example, I could put a briefcase full of documents in the lab and plant a weapon in the Archives so that I could Restore the briefcase to get the weapon out. How I'm thinking it'd play out at the table:

Player: "I'm carrying a briefcase full of documents in through the front door."
GM: "Security checks the briefcase for weapons."
Player: "That's fine. There aren't any weapons currently in there."
Player, later in the score: "I do a flashback where I brought along a ping rifle in the briefcase."
GM: "You're going to need to explain why the guards didn't find it."
Player: "I prepared to be searched by using the Inversion Lab. I put the briefcase in the wayback machine and added the rifle to its history in the Archives. I want to roll Restore to 'revert' the briefcase to the state where it contained the rifle I planted. The rifle wasn't there when the guards did the search."
GM: "That makes sense. You don't need to take any stress for the flashback, since it was a reasonable preparation. Roll Restore to see if you can retrieve the rifle."

Without the inversion lab, I'd probably have to pay more stress or have a better explanation of how I got the rifle in there undetected.

2. Memory Tomb: "+1d to Find and Restore on Site"

I'm guessing it's referring to such checks made inside the "Tomb."

3. Inversion Mastery: "Change the past with a Score"

This one just scares me, but at least it'll take a while before my crew would be able to get it. I'm just going to guess there's a much longer explanation than would fit inside the circle. Of course, it could just be fun having the crew fight cyber-Cthulhu as they do literal time travel by going into the Archives.

4. Message In A Bottle: "When you indulge [Futuresight] by describing an unforeseen complication that will soon affect the whole crew, you may clear 1 additional stress. Also a Mysterious Stranger will assist any one function roll you make - from now until you next indulge this recall."

Mechanically, this is easy for me to understand. It's not so easy for me to get what's going on from a narrative perspective. Is the Mysterious Stranger like your future self hitting World's "rewind almost everything" button and helping you out in the new timeline that results? That's the closest I can imagine without involving "actual" time travel.

5. Stable Loops: While paying the costs of any flashback, you may mark Memory as if it were stress. How do you close the loop?

Mechanically simple, but still confuses me on a narrative level. I'm kind of guessing that from a narrative perspective the Memory expense represents manually changing the past to accomplish the same meta-effect as a flashback.

In some of these cases, I'm just kind of tempted to say, "It's Archive Magic, let's not try to explain it and just get on with the game."