“A young Jedi named Darth Vader, he was a pupil of mine before he turned to evil, helped the empire hunt down and destroy the Jedi Knights. He betrayed and murdered your father.”
The only story necessary for the prequels to tell is the story of a jedi knight who turns to the dark side and betrays the Jedi, then proceeds to kill a ton of them, Luke should be seen by the audience as some random Jedi’s son, and that’s it. There’s no reason to give Luke and Vader the same last name, and there’s no real reason to see Vader’s children being born. When the twist finally comes in ESB, the audience should be 5 movies in and still be in as much disbelief as Luke is, the prequels really could serve the twist rather than take it away. Man, what a shame these movies are.
I don’t know how it’s possible to mislead the audience into thinking that Anakin and Luke aren’t related. After all, Padme is pregnant during ROTS and when ANH starts that will be the obvious connection to Luke. There really needs to be some other Jedi implied to be the one who turns evil.
So what Jedi that we see in the Prequels is capable of becoming Darth Vader?
Maul - Acceptable age, but too short and never established as either a Jedi or Obi-wan’s student.
Dooku - Former Jedi, vague connection to Obi-wan, noble title, proper height. Far too old, however.
Grevious - Good robotification, but again not a Jedi and completely different attitude from Vader.
Windu - Good build and motivation, acceptable attitude, but too old and impossible as Obi-wan’s student.
Of these options, I feel like Dooku has the best chance despite the age problem. If he was masked, and had some sound effects to indicate parts of him were already robotic (and providing an explanation of his stiff movement), he could actually work with some creative editing.
For example, when Dooku is at Anakin’s mercy in ROTS, simply cut away before he is beheaded. Have Anakin say ‘I shouldn’t.’ Then deactivate his lightsabers off camera, with Palpatine saying ‘You did well, Anakin’. This would also make Palpatine not so obviously interested in Anakin as a Sithling. When Obi-wan wakes up in the elevator shaft and says ‘Did I miss anything?’ Anakin could say ‘Dooku.’ ‘Oh?’ ‘His fate will be the same as ours’.