I love the idea of GG = DM.
I think your solution covers the bases well -- essentially, change Maul's name to Grievous in Episode I and exploit all the missed opportunities. I never realized how MANY missed opportunities there are. It is absolutely a natural.
The wheezing schtick didn't bother me that much from GG -- but it was off for most people. The intention was to mirror Vader's breathing, I think. With this DM=GG formula, the wheezing could be made more integral to the story/character. The idea that Maul/GG is a prototype for Vader-- without all the bugs worked out-- is implied and could be interesting. Maybe something to keep in mind if the faltering/wheezing is too hard to eliminate completely.
Anyway, it's a done deal for my alleged future edit. Right along with NO SIDIOUS. Good things!