Most folks I have talked to don’t feel comfortable planning the canon characters (Apollo, Starbuck, Rosslyn, etc). So, I’ve created a Fleet playbook that allows the group to create a fleet of their own, including the rationale for why your fleet is the last remaining survivors being chased down by the Cylons. You can play without the Fleet playbook if your game is going to be on a smaller scale (a single ship for instance) but it’s there if you want it.
I also have a Battlestar playbook, for much the same purpose. When I play a “main cast” game, I use both of them and let the players be the Commander, President and other important figures. They like having crazy power and as the MC that makes your job incredibly easy, as their power also means they have ludicrous responsibility.
I’m not a big BG person, but couldn’t there be additional fleeing survivors? For whatever reason unable to join the fleet? If canon’s the problem, make your own…