This occurred to me somewhere early on in the production where Grevious was mentioned for the first time - even before the aforementioned comic. I thought it would dovetail nicely with TPM, and now, seeing as how Obi-Wan takes him out, it would have been poetically nice. On top of this, Maul would have been driven by revenge (another poetic tie-in) and the fight would've carried more weight.

Honestly, I didn't care in the least for GG. Why was he necessary in the film? I got the sense that he was just an addition that would make a cool action figure. I would rather have been poor Dooku kept alive a little bit longer to fulfill the Grevious role. I mean, he's on side with the Separatists and the Trade Federation already, right?