I think it would be cool to see what can be the back story of some of the greatest companions ( I am thinking of El Toro) that ever lived. Maybe some companions have a dark past, like witchdocters. I want this to be short, so all I have left to say is, think about it. Who do you think will be the most interesting companion?
Sarah Steel comes to mind. El Toro and Mustang Sally would also be good candidates. Any of the companions you obtain through the parents death selection, all of these characters are more developed than most of the other companions you get just out of no where. (no offense meant here KI :)) Now the original characters that can be bought from the crown shop are blank pages, these characters I believe a player can come up with something on their own for their backstory and make for the roleplay pages like this one.