darth_ender said:

I had a thought. Since the new Rebels show has some JEJ dialogue in it, perhaps there might be some useful lines that could get pasted into this edit.

I doubt it as it seems as time goes by they forget how to do their own characters and Lucasfilm forget how to process the vocals properly. As Much as I appreciate Anthony Daniels' dedication to the character he long ago forgot how to do 3PO's voice. It would be lovely to be proved wrong though about JEJ in Rebels :-)