Mattchstick

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Note: In regard to sci-fi expanded universe, this just showed up in Casual: https://www.roleplayerguild.com/topics/168151-the-parallel-campaign-an-expansive-spacefaring-rpg/ooc. Looks pretty darn promising.

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The point isn't to "resolve" either of those things (and at the moment, I don't care enough about the concept to even consider those points of logistics), more to provide a structure that is easier to follow for outsiders, managers of such a context and people within the world itself. It is better, in my book, to try and manage fantasy characters in a setting where relative power can be more easily defined and understood when fantasy typically has specific connotations and expected power levels, as compared to trying to manage an all-encompassing setting where armies with swords and otherwise somewhat primative equipment can meet plasma gun toting kill teams with armor suitable for the thirty-first or what have you century with a pretty clear anticipated result.

Ideally, that's what leveling/abilities are for. But that just turns into a turn-based RPG, and I think we're trying to avoid that.

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I don't see how that framework would resolve the issue of plot inconsistencies, or players abandoning plot-integral characters. If we went down this route, wouldn't we need a lore-keeping and plot-managing staff member for each domain?

Depends how deep you want the lore to be, but I don't see anything wrong with a staff member assigned to each domain. Heck, it makes sense for there to be one specific staff member responsible for each domain.

Even if such positions were created, what would happen if the absent players return to claim their characters?

Simple. Rules and Regulations on absence.

Example: "Absence/abandonment: Players must post at least once per week. If a player stops posting or requests to leave, the GM reserves the right to
1. Permanently or temporarily pass control of the character to another player,
2. Permanently or temporarily turn their character into an NPC controlled by the GM, or
3. Permanently kill or remove that player's character from the story."

Absences can straight up murder a good RP. Make a contingency plan, and make sure players agree to it.

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I had planned to make an RP where people could easily join and leave, with a way to explain their absence and presence. It sadly never went anywhere.

The initial idea was a series of puzzle rooms, with the classic "Everyone woke up here with no memory of arriving and now they have to solve puzzles for reasons idk it'll be explained in the sequel" premise. Inactive players (or players who requested to leave) were killed in traps, new players "woke up in" the current puzzle room with everyone else.

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Hello.

*assures everyone that I have years of experience on RP sites and am subsequently qualified to interject*

As a previous GM who ran a simple open-world RPG, with theoretically infinite options based on player choices, and as a gave dev who tried making a game based on that RPG, I have found that, invariable, players need some kind of plot or story to fall back on. Stick a bunch of kids in a magic sandbox with some toys and buckets, and they'll have fun for a while, but eventually run out of things to do. Even Minecraft, the undisputed king of free-for-all sandbox gameplay, has objectives, achievements, and an "End," so when you get tired of building a space tower out of cobblestone you have something worth doing.

If you're going to have an Expanded Universe, I stress that it have a start point, end point, and a line that leads between the two, so when the Dragonborn gets tired of setting people on fire and stealing cheese wheels, he has something to do that makes progress, even if it just means a new city to steal wheels of cheese from. The line can be a thick, thin, wavy, or convoluted as you want, as long as the RPers have something to, well...you get the point.