system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars Episode III: Revenge of the Sith] If Vader had died on Mustafar, who would Sidious have chosen to be his apprentice?
gpt
I don't think he would have chosen anyone we have met yet. Most likely another powerful force user stolen at birth.

It may also be that Obi-wan tells Luke the truth and trains him, at which point Luke may reveal himself and his identity to the Emperor. Technically speaking if Luke revealed himself, we would be right back to the Death Star II Throne Room with Palpatine trying to bring Luke to the dark side.