Trying to maintain the surprise of the revelation in ESB is a good idea, but pretty much impossible, I think. At least, with the PT we have. Had Lucas made Obi-Wan the main character and had him have another apprentice who is a rival of Anakin, it could have worked. But the PT as we know it made Anakin more or less the main character. So changing his character or arc would ruin (whatever) coherence in the PT's story.

And another thing is, no matter what kind of brilliant change we come up with, we know Vader is Anakin anyway. I think the best we can do is make the turn as believeable as we can. And I think that's quite a challenge already.