You already can play Han Solo, Luke Skywalker, Obi-Wan, Darths Vader though Maul, Boba Fett , Master Chief and James Bond.
But you can't play Leia or Padme. I think the next class they add should be a noble. Before people freak and think this is a gender argument, please don't. One of the common complaints I've heard about SWTOR is that players can't adopt the roles of many of the major character presented in the movies. This includes aliens and droids, who I'd also like to be able to play, but I rank Leia and Padme as more the important character types that feel missing from the game. I might even argue that Lando (aka Baron Calrissian) fits into a noble type better than the smuggler class.
I seem to recall there was noble class in one of the paper SWRPGs and I bet that could be a starting point. I could rattle off all sorts of ideas for a noble class. Leia is certainly ranged dps (next time you watch Star Wars, note that she's the best shot of the three leads), but I can see a force or tech based healing tree in there too.