Bingowings said:

What about merging Utapau with Mustafar?

Obi-Wan is officially there to bring down Grievous who falls to an uncertain end in a lava pit, Anakin is unofficially there to kill the Separatist leaders (thinking Obi-Wan) already dead.

That way you could blur the identity of Vader by insinuating it might be Grievous reborn and still have Anakin (not yet Vader ) fight Obi-Wan because he is a threat to the Chancellor and have a suited Vader enter the Temple and dubbed Lord Vader.

That's not a bad idea but how could that possibly be done? All introduction shots of Utapau would have to be replaced with entering Mustafar (inserting Obi-Wan's fighter, I suppose). All of the scenes of Obi-Wan on Utapau would have to either be heavily edited (and would be a very obvious edit) or, more likely, be completely unusable.

Also, how do you make it seem that Grevious meant anything to Palpatine, or at least enough to bring him back to life (apparently for a second time)?