I think it would be cool to have several classes available to both sides.
Republic Agents - an SiS storyline could be fun.
Republic Bounty Hunters - Why not? Bounty Hunters should be neutral anyways.
Empire Smugglers - You know smugglers worked for the Empire too.
Empire Troopers - They obviously have Imperial soldiers
I know that some classes are supposed to correspond to the other side, but the abilities are not all the same and they play quite different. I just think it would be fun to have more variety.
Troopers in the Empire were cannon fodder, while the Republic was more elite.