I’m working on something similar right now where I’m essentially making the longest possible canon cut of ROTS. The plan is to have lines from Battlefront 2 replacing the clone and grievous voices in the 2003 CW and every deleted scene incorporated as well.
I’m also planning something similar for the clone’s voices, hadn’t thought to do it for Grevious though, good idea!
I think these ideas are pretty cool and I was thinking of something similar. I would probably use a straight extended cut of RoTS instead of the New Canon Cut though, just to keep things as close to true canon as possible and appeal to people who want the longest possible cut.
I considered that briefly, but personally I really want Anakin to feel consistent between the different source material and no Theatrical or Extended cut of RotS is gonna do that for me, though I’d probably still watch a “ultimate” cut like that.