I like the R2 recoloring. Always strange that the droids were in the PT. If an edit made it so he had a different name (R4?) and this recolor it would probably work.
R2-[something else]? It would make the most sense in-universe and would avoid having to redub most lines. Captain Panaka reads out his full name in his introduction scene, so it would be established right away it’s not the same droid.