I've been thinking about this for a while. Where the hell was Rebecca Chambers after the events of RE1? If it were up to me I'd make a side game with her escaping Raccoon City. For the first half of the game your partner would be Brad Vickers. (Before you dismiss me completely, this might make a little bit of sense!) Perhaps they could have their own side story and they end up getting split up because of the nemesis. Rebecca then runs into Billy (because he's making his way out of the city too) thus making the second half of the game.
Maybe they make it out of Raccoon before Jill, Claire, Leon and Carlos... or maybe they don't make it out at all. (
not a great ending, but might be more realistic.) Who'd like to add onto this insanity with more ideas? 
Maybe they make it out of Raccoon before Jill, Claire, Leon and Carlos... or maybe they don't make it out at all. (

