Anakin is only desirable if he is the best. Why would Sideous lament the loss of a loser who couldn't beat Dooku?
He lost to Dooku countless times. He even lost to Obi-Wan. Sorta.
I think that his role in Palpatine's plan is a little more that being a killing-machine. He is the Chosen One, after all. There are even rumors that it was Darth Plagueis, who created him.