I like the idea of Vader disappearing while still Ben's apprentice and then returning as a Sith Lord

I actually would've liked to see anakin & ben be great friends who slowly grow apart as their beleifs & ideals about the situation of the galaxy diverge over time. While palpatine would be a key influence in anakin's turn, i think it would've worked really well to actually have the official "turn" be in a final heated arguement with obiwan that devolves into the duel at the top of a volcano. Then, he wouldn't actually become darth vader until he's encased in the suit after being rescued by the emperor. This would also seal his loyalties b/c obiwan would have left him for dead right after the fight that sealed the deal of his turn, while papls came to his rescue. It would also mean he wouldn't kneel before the emperor in some confused, awkward moment, but with total loyalty. That would actually make a cool "chrisening" scene. Right after he's been rescued, the first thing we see him do in his new body armor, would be kneel before his new master & pledge his allegiance. You could really make it a chrisening by having him named Darth Vader in that scene.