Dooku in TPM: Dialogue on the com link is good in concept, but remember: "Send to transmissions of any kind." I doubt his communicator razor would have the range anyway. Talking with Yoda and Mace could be made possible by utilizing the scene with Obi-Wan contacting them via hologram about Kamino. I'm not saying to do this, but that is somewhere to start if you want to experiment with the idea. Personally I think TPM is fine without Dooku, especially if we're keeping the mindset of Episode I being a standalone introduction to a six part saga. There is proper set-up and backstory for the character, and we understand his significance.

Grievous is a completely different situation in that he comes out of nowhere and suddenly becomes the end-all be-all of the Clone Wars. The thought of making him Sifo-Dyas crossed my mind as well, and though it would indeed answer who ordered the clones, in the end it would cause more questions than answers. The pay-off of him being Maul is infinitley more intrguing for both the plot and the character himself. I totally agree if we can't show the birth of Grievous professionally we shouldn't show it at all. That said, I don't think that would make it necessary to scrap Maul=Grievous totally. I still believe it can work without SEEING the procedure or whatever, and should at least attempt that route.