I know this might sound stupid, as something similar was suggested over on the “Worst Edit Ideas” thread, but what if, when C-3P0 got his memory erased, his voice were replaced with something flatter, like a text-to-speech? Then it would be easy to replace his dialogue with something less… Threepio. It would be like fully erasing his memory had also removed all of the personality traits he had picked up over the years and made him act like a totally different character, which would feel more like a sacrifice.