So say I wanted to run a Traveller campaign. And say I wanted to do it with an irregular player base-- potentially a large one, and potentially one divided between an online and an offline group, or even several offline groups.
One option would be to do like Jeff Rients and have everybody be the crew of one big ship (or other relatively stable focal point). Divisions in the player base (as opposed to simply irregularity of attendance) can represent either different shifts on one very large ship, or the different crews of one or two different ships.
This solution is a pretty good one, but the problem with it for me is, I haven't run a lot of Traveller, or played a lot of Traveller. If I'm going to run Traveller I want to do "normal" Traveller and explore that for a while, and "one massive ship with a giant crew" feels too high concept for me. I think of Traveller as a game about independent operators, probably with their own small ship, trading and fighting their way across the galaxy. "One big ship" would be a cool campaign, but it seems more like "Traveller-- the Trek way" or "Traveller-- the WH40k way" than straight up, old-fashioned, truck-drivers-in-space Traveller.
So what to do?
A potentially much crazier option would be to just have a big player/character pool of relatively "normal" Traveller characters. If they've rolled up ship shares or enough credits to buy into a ship, then they're attached to a ship (maybe the same one as a few other characters-- they can work that out themselves at character creation). If they haven't, then they're independent operators-- freelance mercenaries and the like. I keep track of what system each ship is in, and when, and which characters are or were on each ship.
Whatever offline adventures I run are assembled in the normal fashion. Online, sometime before every session I randomly determine which character is the "expedition leader" for that session, in the manner that I think Zzarchov was using at one point and the way Jeff is running his magical Mormon campaign. If that player has a particular mission they want to execute we can do that; otherwise, I hand them a couple of patrons they've been in contact with recently and they choose one. Then they're in charge of getting together the rest of the group to take on the mission. They can add anyone from their character's ship, and anyone in the "shipless" part of the pool (we'll come up with some explanation for how they came to be working with that group that week). They can add characters attached to other ships (and potentially those second ships as well-- sometimes, you just want an armada) if they're close enough by that it makes sense.
With a small group this wouldn't really be necessary, of course. You'd just have the one ship. But the method of "select mission lead" and "mission lead selects mission" would still be useful, I think, for focusing the sessions themselves so you can get to the action quickly, and so that I have a day or two to prepare.
With a bigger group, you'd just have a handful of ships tooling around the subsector/sector. There'd be a bit of paperwork to keep all the ships and the characters roughly on the same timeline and to keep the world integrated, but I think that's a doable with a variation on the system Ben Robbins used to keep track of his incredibly complicated large player-base superhero game.
The really neat thing is that this opens up the possibility of having a bit of a trading sub-game for Captains of ships and other interested players-- between sessions, by e-mail, they can direct their ship's movement and buy and sell and whatnot. If they don't turn in their moves before I need to normalize everyone's locations for a session, then I can just say they were shipping standard freight along normal trade routes.
I'm not sure yet if I'm actually going to pull the trigger on this. I spent the weekend getting to step 11 on Rob Conley's Traveller sandbox guide, so there's definitely some enthusiasm for this potential campaign. At the very least, it's something I want to have in my back pocket for if I'm ever called upon to run a quick one-shot. Eventually, I want to have a binder containing a Traveller scenario with pre-rolled characters and a megadungeon suitable for brand new players, so I can take that baby with me and be ready to game with a couple of options wherever I go.