maybe you don't necessarily have to be following the training and upbringing of palpatine, or vader. You can follow a Sith from the old Republic, living in hiding and secrecy, you find a powerul force user, and bring them to the dark side. Then they are trained from being a weak and scatterred being, to a piece of iron, a cold hard killer, something capable of overthrowing an entire galaxy. Maybe better for a movie or soemthing like that, but a game would be interesting.
The very existence of flamethrowers proves that some time, somewhere, someone said to themselves, "You know, I want to set those people over there on fire, but I'm just not close enough to get the job done." -George Carlin