I'll be finishing my rewrite of Episode III when I get home from the US (I'm in Seattle now and I live in Australia).
The idea that I like the most is Anakin having to harness the dark side of the Force to sustain himself. Although, I would have done it all in a slightly different order.
- Obi-wan dismembers/mortally wounds Anakin on the volcanic planet.
- Obi-wan returns to his ship (I don't know if it works to have Padme there or not), is alerted to approaching vessels.
- Obi-wan leaves to evade ships that he thinks are looking for him. Obi-wan escapes.
- Palpatine arrives in one of said ships. He finds Anakin, dying.
- He tells Anakin that he must harness his anger and hatred to sustain himself.
- Anakin sustains himself with his dark power.
- Palpatine takes Anakin somewhere where they can operate on him.
- Anakin is given the suit and a name. Darth Vader. (that whispering thing was a good idea, I think).
- His new dependence on the dark side effectively kills his old self.
Or perhaps Vader's name doesn't need to be said at all, and it can be merely implied that he adopts the name Vader over time. But I do think that Anakin probably should have became Vader upon being roboticised to give weight to Obi-wan's claims that he is more machine than man, twisted and evil. Obi-wan kind of implies there that his dark power is at least partly attributable to his inhumanity (although, in a way, Luke disproves this in turning him back). But one thing's for sure, Obi-wan's OT monologue left no room for a Darth Vader that wasn't robotic.