I seem to recall a long time ago a Babylon 5 group game. I'm not sure it got off to a strong start. It would be interesting and I think people would jump on board with the scifi fans around.
Hmm... The problem with people jumping on to B5 is that it spins and they get spun off again!
That was a rather oblique way of saying that B5 is a very specific environment, and unlike Star Trek where you can have a fictional ship with a fictional crew, B5 has a specific list of canon characters. I can see a lot of people going "oooh Sci-fi", and then realising that it's very specific and either dropping out or no even joining.
So you either go totally AU-B5, which almost defeats the object, or you specify that all characters are to be non-canon. The thing about B5 as opposed to a Trek starship is that on B5 there is a constant flux in the population, so bringing new people in and loosing drop-outs is easy. And you simply state that all canon characters are GM controlled NPCs.
I think that works quite well.
Now all we need is someone bold enough to try running the game as a sandbox... (Or perhaps a spinning steel cylindrical box?)