RogueLeader, I really like what you proposed! It does involve some creative redubbing, but it seems doable (Auralnauts’ videos made good work of it). Keeping the surprise does eliminate some of the more “emotional” parts of III, but I like that it keeps Anakin’s fate ambiguous while also presenting some ambiguity over Vader. There are a few points I’d suggest:
I: You mention the idea of making Obi-Wan a full-fledged knight - I think that you can make the element of doubt work through redubbing the council to hint that they’re aware of Obi-Wan’s failure with “Vader” and are reluctant for him to teach again. Heck, Maul/“Vader” could be evidence that “too old” apprentices go bad. It would be Qui-Gon vouching for his former pupil instead.
II: I’m not sure what exactly you’d cut from the Anakin stuff on Tatooine (easing PT-OT inconsistencies. It would likely depend on what you do with TPM.
III: I would suggest showing Grievous or Palpatine looking at a bacta tank at some point. If it’s clouded enough to hide the person inside it, you can imply that it’s either the apprentice or Grievous’ empty tank. That way, it keeps up the mystery. I like the idea of calling both Dooku and Grievous “Darth Tyranus” and Maul/Anakin “Darth Vader.” It does prove to be an issue with the “Rule of Two,” but removing said rule really isn’t a problem for editing (compared to the redubbing and some visual changes).
Adding Obi-Wan picking up Anakin’s lightsaber while examining the temple ruins could also work to explain how he gets it for IV.
While I do agree that this is far more work than simply changing around some episode numbers on the crawls to make it go ANH-ESB-ROTS (or a three-in-one edit)-ROTJ, it’s still a worthy venture. Good work, RougeLeader!
JEDIT: Perhaps Mace goes to face Palpatine, cutting to Anakin’s flight to the office once we see Palpatine draw his lightsaber. We keep the ruminations scene in, as it’s an important emotional beat.