To remove 3p0 from the story, all we need to do visually is remove him from the interior space ship shots as Anakin and Padme decide to rescue Kenobi.
After that, I think we can cut around his shots entirely. As far as I recall, we only see him again on the same space ship telling R2 that he won't be going out to help save Anakin.
If we re-dub the grey, sun-baked protocol droid at Owen's farm with a robotic voice that is clearly NOT Anthony Daniels then he can simply be one of the droids on the farm. He can be at the funeral and even say the line, "He's carrying a message from an Obi Wan Kenobi. Does that name mean anything to you?" It may work better coming from a different voice anyway.
Just saying. Not a big deal because TM has already made 3p0 so small in the movie that he almost causes no pain. The biggest problem he poses in SOTDS is in attempting to un-do the idea that Anakin built 3p0. If we eliminate 3p0 altogether, it also makes this ambition possible. A new TPM edit could be done which eliminates 3p0 from that movie too. Hmm.