The Traveller game hasn't started yet, but it's coming along. I'm most of the way through my starting sub-sector, and I've started sketching out the larger political situation. Nothing detailed, mind you. I just needed to know who was running all those spaceports, if there's no Third Imperium in my Traveller universe.
The answer is: another sort of space empire. So far mostly cribbed from Dune, but I'll add in other bits as I go along. Combined with at least some of the Class A and B starports being alien relics, run by robots, this satisfies what need I have for the setting to make sense. I'll make up for it with the planets -- I still need to figure out a place to put the Red-Eyed Cat-Apes.
I am, though, struggling with how much detail to put into that upper-level political situation. I'd like to keep it as loosely defined as possible, partly for philosophical reasons, and partly to avoid doing work. I do plan on making up a minor noble from a minor house (noble houses being the main thing I'm stealing from Dune) to be governor of the sub-sector, and eventually I'll work out a few rivals and allies, to aid in the generation of schemes and plots. But there's no need for a big list of all the houses and nobles and all of that.
Except that I had this idea, that if each of the houses has its own army and so on, then some of the characters might have pre-existing allegiances to them, or old grudges or something. Which would, then, necessitate some manner of list. Unless the players could manage to make something up on their own, if the idea interests them, but I've had mixed success with those sorts of schemes.