brash_stryker said:
Retain Hayden's fall, just make him a different person. i.e. not Anakin. Remove the chosen one aspect, and remove Padme having babies.

That way, he's still Obi Wan's student, but assumed to have become Darth Vader. Then it is revealed in Empire that its really Obi Wan's good and loyal Jedi friend, Anakin (whom we never see in the PT)

Can you imagine how shocking that revelation would be? We're all under the impression that Darth Vader was the little shit of a student we saw in the PT, but it turns out to be Luke's dad!

It would make his unmasking that much more coherent with the PT (seeing as Sebastian shaw looks nothing like Hayden Christensen).

So... we'd watch 6 hours of young Obi's adventures with some guy who ultimately doesn't matter, never meet anyone named Skywalker,and then when he talks to Luke in "Star Wars" he'll refer to his good buddy Skywalker that we've never heard of. Then in "Empire" we learn Vader is Luke's father.

My first thought would be 'WOW! Unnamed guy with the eye-scar was really Luke's father!" not "Wow, Luke's father had the exact same character arc as eye-scar guy but is totally unrelated and so unimportant as not to be featured in the last three movies."