I don't think bastilla and Raven will fight eachother .
The problem with making a part 3 is because the previous 2 had alternative endings .
So 2+2 = 4 means you have to begin with 4 different options , and this time i think not even a small conversation with a spaceship prisoner will do .
I suggest the same hero's as both previous games ,(except mission and the wookie, unless they survived, you killed them in part 1 i believe)
I had a concept written down a long while ago .. i'll post it later perhapes .