I wanted Obi-Wan to believe Anakin was dead, it seemed very wrong for him to just leave him there to die. If he could be saved it would have made sense for Obi-Wan to have saved him and brought him back to the ship. In his mostly limbless state he wouldn't have been much of a threat. Just seems like the thing to do for somebody you consider a brother. If there was a way to edit it so that as Obi-Wan stares in horror he sees Anakin "die", then turns away in disgust and grief. There is a shot of Anakin's robotic arms moving. I found fading the screen on this gave it the hint that he lives, without giving away the farm away with the Frankenvader scene. Of course this would also require a bit of minor editing to remove any lines of Palps calling Anakin "Lord Vader" in any of the scenes before the battle of the heros.
It would be nice if the film could be vague where Padme has the babies. If there was a way to show her having Luke, then ending the scene and not killing her off, that would be great, but really hard. All the end material of the film has to do with the creation of Vader and the birth and distribution of the twins. Padme living and Anakin's fate being unknown would mean no funeral scene, no Lars scene, and no Star Destroyer scene. It will be hard to keep from making the movie seem cut short. Perhaps we could show Luke's birth, then Padme dying, then have Obi and Yoda talk about needing to hide the baby and showing Obi-Wan wisely taking him to live with the Lars family while keeping the name Skywalker, binary sunset, the end.
Just what I had been working on doing with my edit. If this could be done, and some people here have done some impressive work before, so I think it might be possible, then this would somewhat preserve the surprise of "I am your father" (I really think this is about the best we could do on this front) and it would completely preserve the twins surprise. There are still a lot of kinks, like the pupil named Vader who killed Anakin that would need working out, but since this is a saga edit that is easily enough fixed with some editing in ep 4.