Wow, that is exactly what I was thinking of doing....
So how did you solve it? using an external coxitron control from a Pelco matrix? or using the serial command and sending the analog out to the esprit ?
I am going to try this type of implementation next week, I know Axis has their own pan/tilt head, but we already have some of the esprit from Pelco, and they have proven themselves as very reliable for many years...