I always thought it would have been cool to have Dooku realize he was just a tool to Palpatine, and he somewhat suddenly turns back to the light side at the last minute and 'just in time' saves a vital character's life from the saber or Dark Side powers of Sidious and dies in the process against Palpatine during a massively cool saber duel.
I always liked that idea, and somewhat expected something like to to occur in III before it came out, oh well, his death is cool enough how it really happened.