Prune face Palpy is actually a very good idea if you go the upfront route that it is Sidious pulling the strings. Or you could go the mysterious route and darken the features under the hood to leave it ambiguous.

Or maybe you don't have any communique with Palpious at all and just leave it to the Neimoidians and Maul during the first film?

Then maybe have Maul say something about a master during the end duel so the jedi know Maul is just the apprentice and the Mastermind is still out there?