First off let me address the concept of making General Grievous into a resurrected Darth Maul. Clone Wars Cartoons aside, GG is an incredibly lame plot device of a character. He comes out of nowhere in RotS and is treated like the end-all be-all of the Clone Wars. That would have been fine if he had been established beforehand (in a FILM, not a cartoon), but as it stands now his characters seems nothing more than an afterthought. Not only that, the annoying coughing and ridiculous cliche dialogue take away from what could have been a menacing villain. So GG was a definite weak link in the RotS chain. Much has been made of the PT suffering from a lack of consistent villains, outside of Palpatine of course, and it’s true. This attributed to the prequels not feeling much like a trilogy at all, especially not in the same sense as the originals. RotS tried to rectify things with several connections to TPM, and it was a valiant effort which they almost pulled off. But can you imagine the drama/hype that would have resulted if Darth Maul himself had returned in a cybernetic body commanding the Separatist forces? Great stuff. I can’t believe Lucas didn’t think of that angle when conceiving Grievous. The manner of Maul’s death makes it easy to believe what was left of him was transplanted into Grievous’ cyborg body. His yellow eyes tie things together nicely, as well as his lightsaber skills. His guards’ double bladed vibroblades also contribute to the theory, a throwback to Maul’s original double bladed lightsaber. So that’s the concept.
Now onto the logistics. I know that RS’ plan is to remove Sidious from TPM, but assuming it wasn’t, replacing his mentions of “Maul” with “Grievous” would set things up perfectly. I prefer the name Darth Maul to Darth Grievous, but taking RotS into consideration there’s really no other way to get around it if you want them to have the same name (which I think they should). As for RotS, dubbing over GG in a deep, mechanically altered voice shouldn’t be too difficult. That’s the beauty of his lack of a mouth. The coughing would have to be eliminated as well, if for nothing else than the annoyance factor. Dialogue would obviously have to be altered, making references to his defeat by Kenobi, and having that serve as a character motivation. I’m sure someone could come up with some applicable dialogue. Either way it would be impossible for the Jedi to know this was the same Sith who they encountered in TPM, so Grievous would need to reveal this to Obi-Wan in their duel. The close ups on their eyes would be the ideal spot, as new Obi-Wan dialogue would need to be inserted as well. This just adds so much to the Obi-Wan/Grievous confrontation as Kenobi is again facing the man who killed his master, and on Grievous’ end, a chance for revenge on the Jedi who crippled him. Also the parallel of Obi-Wan hanging off the edge of the platform gets a lot more parallel when it’s once again facing Maul. I think Grievous’ lightsabers should all be red, since he would be an official Sith, but I know it would be a pain to rotoscope. I like the concept of him collecting lightsabers but now that he’s Maul that aspect wouldn’t fit (he obviously doesn’t keep them as he kicked Obi-Wan’s down the reactor shaft on Naboo). The conversation with Sidious in RotS would have to be reworked considerably, addressing him as “Lord Grievous,” but I don’t know how to approach his mention of making Anakin his new apprentice. Maybe a mention of destroying Obi-Wan as one of GG’s objectives, as Sidious trys to get rid of him (and thus his positive influence on Anakin) for most of the film. As for the rule of 2, you could always go the MagnoliaFan route and make Dooku a rogue Jedi with no affiliation with the Sith. That wouldn’t explain the three villains’ connection in RotS though. Cutting Yoda’s line down to, “Always two there are, a master and an apprentice,” would do away with the “rule” and make it more of a concept; it’s assumed that if there are more than 2 of them, the Sith will try to kill each other. This would all tie in nicely with the situation we have in the OT: “He would be a great asset,” “He will join us or die,” etc. Sidious has no problem with taking on more than once underling if it suits his purposes and he remains in charge. This dies beg the question though, what’s Maul up to in AotC? Working some Grievous into Episode 2 in some capacity would be great, but that’s something I’ve yet to come up with. One other point, in regards to everyone addressing him as “General” instead of “Darth,” Obi-Wan is also a general (add that to the Maul/Kenobi parallel list), and is called as such. Also, the Republic at large might not even know Grievous is a Sith, and as I noted before there’s certainly no way for them to know he’s the same Sith from Episode 1.
So those are my not so brief suggestion on how to make Maul into Grievous, strengthening both characters and the prequel trilogy as a whole. I eagerly await your feedback.