Remember in Revenge of the Sith with Palpatine was telling Anakin of some power his former master achieved. Using the midichlorians to create life and that in achieving this power keeping someone alive would be much similar or however it was put.

Could Vader of discovered this power, kept it from Palpatine and used it on Starkiller after the final battle events on the Death Star in the first game???

Vader tellinging Starkiller he is a clone could of been a way to cause self-doubt. And maybe what Vader said in the beginning about force user clones going bad was true. We did see clones in the final level and they didn't seem very sane or stable(although they weren't matured clones yet).

Many of the star wars ideas for the expanded universe seem to focus on alot of prequel knowledge. This may be the secret the game developers might be keeping for the 3rd game revelation(if there is a 3rd game).

i dont think vader is powerfull enough and patient to learn such a secret and probably hard technic.. (although he might have been strong enough before he nearly died and had to wear the suit and everything..)