TMP - Age up Anakin to about 17/18.
AOTC - Give Obi-Wan another pupil, who is also tempted towards the dark side.
ROTS - Make it look like Anakin and the other pupil die about midway through the movie, with proto-Vader (mask, but no life support suit) taking his place.YES to all of these, though I don’t think “no life support suit” is necessary for act 3 EpIII Vader.
I could go either way with that. My thinking about that final duel on Mustafar would be to have Obi-Wan fighting pre-suit Vader (mask with vocal distortion, but no breathing sounds or extensive cybernetics). This Vader, who is never linked to Anakin other than saying he destroyed him, would fall to his near-death onto the embankment of a lava river. This injury would render him quadriplegic (per the technical commentaries), leading to the immolation and the necessity for the suit. It could also be a way for the “Obi-Wan once thought as you do” line to make sense, as Obi-Wan tries to reach out to Vader and Vader chooses to fall to his death (I got the idea here). It’s like poetry, it rhymes! 😉
If we go with the “he’s already wearing the suit” option, perhaps he fought the other pupil and they both sustained substantial injuries before Palpatine intervened. With it left ambiguous who truly lived, Vader would seek out Obi-Wan and Padme. Padme would plead with this new man, trying to persuade him to come back to the light. He tries to kill her before Obi-Wan intervenes and starts the fight. Vader could also be immolated again here or trapped in something to allow Obi-Wan and Padme to escape.
Keeping Vader a mystery man in Episode III should have been a goal of the prequels (same with keeping Yoda off-screen and allowing Padme to survive the prequels on Alderaan with Leia). I like it when fanedits cut out Vader’s name and suit appearance from the film.