Few questions to GUNINANRUNIN:
-Does the crew have extended lifespans or undergo cryo-stasis? (At 70% of c, it would still take over 6 years to reach the Alpha Centauri system, is that intentional?)
-What are the relative distances between Sol, Marlowe, New Hope, New London, Kulan and Shotel? (If that is covered by "GM Note: More on this later", just disregard this question.)
-Are there specific ethnicities that are associated with the various systems, or was colonization a U.N. free-for-all?
-Do the various systems have separate currencies, or are they all part of a stellar E.U. arrangement?
-Do we all collaborate to design our captain or do we submit our ideas individually?
No, no gene modification shenanigans. I'm not a fan of biomechanical stuff, I'm mostly fine with implants and prosthetics though since there's a good amount of evidence today that they'd work. When it comes to inter-system travel the crew
could just sit on their butts for 1-20 years to get wherever they need to go, but they have stasis (probably cryo or something) for that kind of thing. We took relativity into account so most of your adventuring is going to be happening in one system, that way trips will last only a few months at the worst and we don't have to worry too much about time dilation. I'm totally fine with you guys going wherever you feel like but if you need to jump system I'd have to take some time to plan for that in advance. Just don't get in trouble with the space navy and you'll be fine.
Gig is working on some detailed information about the colonies, but my impression is that each colony is in it's own respective system. More on that later.
My answer is slightly roundabout but bear with me: after the Screenshock genocide Mars took measures to ensure the security of the human race, one of them was pushing out the sleepers. At the time everyone was losing their shit over the 10 billion people who just died in the space of a day so the public was really behind the idea. The only problem was that people were far enough away from the danger that they were falling over each other to be put to sleep on a space ship for 100 years, so they encouraged civilians by offering the inhabitants of the sleepers independence. Whatever worlds they claimed they would govern, this was a pretty awesome and clever idea considering that FTL communications are not a thing. News only moves as fast as the Lightpushers; inter-system administration would be impossible. So Mars government put in a few clauses naming their world the seat of Humanity but otherwise just shot millions of people into space and ordered them to do whatever the hell they want.
Everyone uses spacebucks, everyone speaks English at least. There were standards put in place as part of the agreement to the Confederacy. The politics vary but the structure is the same wherever you go. Every colony has a space police and all the citizens get to vote.
All these chars are PCs. You can submit a sheet either for the Captain position or as a member of the crew. I pick my favorite submission for the Captain, then he gets to cherrypick from the crew submissions to form his team. You're absolutely allowed to make changes and tie your bios together, work on interconnected backstories in the thread and the like.
EDIT: I didn't answer your ethnicity question did I? Mars was a UN mission and the sleepers came from there so the colonies are going to be a healthy spectrum of races, though inevitably some places have a dominant ethnicity (Rule Britannia! Long live the God-Queen!).