Bingowings said:

What are you if you have none of your prior memories (everything in your head from birth until now gone)?

Are you you or are you something new?

Right, but I'm a human. Obviously droids don't work that way.

We have already seen that droids identical to Threepio can have female voices and we have speaking devices where you can manually shift from a voice type in the real world.

Getting rid of Anthony Daniels in the PT provides a blank slate for an editor to build a more functional droid personality which could be lost in the mind wipe.

Right, it's useful for editors.

Which would be rather tragic for a droid the audience has come to care about.

We are meant to care about the droids more than their owners do, that much is obvious in the writing of the OT.

I guess so? One of the failures of the PT is that Artoo & Threepio are not the main characters the way they are in the OT. Completely replacing one of them with a different character (albeit in the same body) doesn't really help this.