No, they're completely different classes. That would be like changing from mage to warrior. This game's leveling is so easy / fast too, you can just level another character. They're all mirrors on the other faction too. If you have a Sith Marauder but want a Juggernaut, make a Jedi Knight and play Guardian, it's the same thing but a different story. Otherwise, if you still complain it takes too long, you might want to find a new hobby such as casual phone games.