Eliminate advanced classes, and combine their coolest powers. I don't want to play a Merc or a PT. I want to play a BH. I don't want to play an Operative or a Sniper. I want to play an Imperial Agent. This would make the classes more fun, and also eliminate the drudgery of having to decide which advanced class to play, effectively breathing new life into the class system.
Of course, I've been playing less than a month, so my idea is probably hideously flawed.