A new player doesn't know how the Sith Warrior or Inquisitor story will go anyway.
You could always add a 3rd Advanced class.
As I understood it my Sorcerer can't become a Marauder. If I want to play Assassin I have an alt for that. I can understand it for people who don't want alts and now have technically 4 advanced classes as a Sith.
Still, I don't see the overall benefit of this feature. Will it bring old players back and new players in? Still, only thing I want is weapons in the outfitter.