Bingowings said:

It might work if in the scene where Dooku talks to Sidious at the end of AOTC Dooku was replaced by Grievous.

He is the Seperatist General so having him turn up at the end to proclaim the start of the war could create a mystery about the new character and make us start to question if Dooku really is in charge after all.

It would be an interesting twist if Dooku doesn't know that Palpatine is the Sith Lord until the moment he orders Anakin to kill him.

I can almost see that being done.... but only by using footage from ROTS when he's talking to Sidious on the hologram. You could easily take Palpy's lines from AOTC and insert them there, but we would need Grievous saying "The war has begun!" We don't have that sentence at the moment... If I could get someone to do his voice saying that, I could totally make that work.