Monroville said:

I also like the idea of not even showing Anakin becoming Vader... just end it with him burning (take out the last moans so he goes quiet, ie. audience thinks he's dead) and Obi looking on. Then (as Muddyknees I believe wrote) you see Vader in ANH and go with it. That way when you get to EMPIRE and Vader does the reveal, the kids go "Holy Shit! I thought he was dead!" Combine that with the whole "fake Harvey Dent-ish" funeral, and it makes Obi Wan and Yoda a little more dimensional as characters.

If you go that route, then you also have to take out the whole "A pupil of mine named Darth Vader..." speech Obi-Wan gives in ANH. Because it would be pretty obvious that he was talking about Anakin if one had seen ROTS.