yeah, I suggested something like "Jekyll / Hyde", with the touch of supense and mystery, the story plus the "turn" would feel more natural - Anakins broken psyche and his lust for power should have been the vehicle to introduce the dark side of the force ...
hm, the duel could be us seeing it through Anakins eyes, by this time he is twisted, but not completly evil, Obi-Wan is the dark spectre we think killed the other Jedi, in reality it was Anakin all the time!