I suspect the idea for removable panels on 3PO came about so they could use this basic protocol figure mold. Lucasfilm has, up till now, insisted that all C3PO figures use the vac-metal look. Hasbro has wanted to use another mold that incorporated more articulation; but the vac-metal process made it difficult, if not impossible, to carry out. It was probably a matter of adding something extra cool (subject to interpretation of course) so they could get the approval to go with a non-vac-metalized look.