These characters only work in the context of the series. They are citizens of their society or it's mobile semblance. Anything additional would be pretty dull. Baltar and Caprica turning into American Gothic? Apollo turning into Grizzly Adams? Helo and Athena's little house on the Prairie? Doc Cottle, Medicine Man (and tobacconist)? Nah. It's over. I wouldn't mimd some fiction about the years before the fall of the Colonies, however. There must have been some stories to tell. The crew seemed to have plenty of combat experience beyond just training. How'd that happen?