But in your story, your opponent will always be evil. That's something I really don't like. You can play good vs. evil and evil vs. evil, but you can't play evil vs. good (from the evil perspective).
I don't think this is always the case with SWTOR. For example, in the Sith Warrior storyline whenever I faced Jedi it was very clear to me that they were the good guys and I wasn't. When the Sith Warrior fights against rival Sith, yes, then the enemy is evil but even in this case it's evil vs evil.