I'm going to get behind bingowings suggestion that Maul and Greivous = the same person.
If done correctly( a tall order I agree) it will strengthen the entire PT narrative IMHO.
edit
What if Mustafar is a hideout for the Sith and the buildings and everything are sithy?
Sidious could send the seperatists to hide on what they think is a safe haven, his own hideout.