I was actually going to suggest using another Sidious hologram scene in just substituting Maul in the close up. Good call. The Nute/Rune (actually that's not Rune, that's the "slime" guy) exchange doesn't quite work in front of Grievous though. Maybe MTH or someone else can come up with some new dialogue (you're right about the body language, btw). Grievous dialogue in the long shot works great too, working out much better than coming from offscreen, which would really expose the cut-and-paste nature of the scene. Overall good job. I would suggest slowing down the footage of Grievous' close-up though, as he shifts too much in the limited clips we have. Drawing them out more would correct this problem.

Here's a crazy thought: Since the Maul/Sidious swap worked so well and everyone's big on Dooku being in Episode I, what do you think of some Saruman dialogue in the Sidious shots, with the close-ups of the hood darkened like in MagnoliaFan's version? Just a fun experiment to mess around with. It's too bad we don't have any shots of a Grievous hologram though; that would be a good way to incorporate him in Episode II.