It's a little hard to list this out~ It's not some short story with a beginning of an end. It's a huge, whole new world that has to be made. This could just go on forever. It's an MMO after all.
I'll concisely list out the basics, so you can keep them in mind for any ideas you have:
-Everything takes place in a whole new solar system, with dozens of inhabitable planets and moons.
-It is toward the end of the 21st century, following people generally becoming more and more sexually liberal.
-The one bit of "magic" is that FTL travel has something to do with sexual energy. Doesn't make sense, but magic.
There are only so many options for near term colonization, such as a generation ship. But a generation ship would be one big load of people at the start, when I need something for them to trickle in, a bigger population, and so on.
-The aliens physiology is susceptible to terrestrial DNA, creating sol-alien hybrids.
-The start of the story starts a generation or so after the new solar system started to be inhabited by humans. It's just long enough for sol-alien hybrids to still be finding their place. It's long enough to have habitats made in various places, but not to have fully built cities. -There is lots to explore and discover.
-Time will probably be accelerated 12x, since this is an MMO and real time(thus, no sleeping to skip a day, or turns. Instead, daytime and night time will probably last one hour each).
-There was not highly sentient life in the solar system prior to humans. The humanoid aliens are all hybrids of humans. That's not to say all the feral aliens are dumb; there can be some are just humans intelligence.
I'd say just leave it open for interpretation until you or whoever is going to do the majority of the writing is comfortable with the setting. Explaining things like that isn't really necessary for the game's scope; it's perhaps an interesting detail, but it probably won't have an effect on the game itself. So later, if you decide to make things different, you can just introduce new details instead of retconning stuff.
In-game time sounds good. Personally, I'd like a tad more leeway, so you could have NPCs with full schedules that the PCs can follow -- when they're at work, at home, asleep, taking a walk through the park, etc. But I suppose shorter cycles can work just as well, the PC will just have to come back on a different "day" (that is, wait a few hours) if they're looking for a particular event. Perhaps there can even be different cycle lengths depending on what planet/asteroid/space station/moon/etc you're on and how fast it rotates or artificially regulates its day cycle, though that may be unnecessarily complicated.
I'm separting "sleep cycle"(24 hour period) from day on all the different bodies. The different planets/moons do have different day periods that are listed, but how long people are asleep or awake wouldn't change, except maybe for native things.
You can see this in Outpost 833, where days are longer than the human's cycles on the logs.
I don't think I'm going to do schedule things, like there being weekends, since there will be enough changing by interacting changing. But who knows.
I can already imagine the ships having some kind of sex machine style seat that is activated when you start the jump drive.
Might look something like one of these.
It goes faster and faster as it's charging up and then jumps when the user climaxes. XD
Sounds like some fun ships to fly.
And yup there will probably be some lewd plug suits or chair somewhat like those.