Well, I may be having to do something like this son once the ServoCAT goes on the the big scope. The movements do not have to be so precise as those in Alt/Az, I have been considering using at ST-7E or similar - with the guide chip deciding movement in all three axes. Very early days though...
Arthur
PS - meade derotator (or derotater as they call it on the item itself
) is up to 14" since the bigger scopes have different fittings - nothing more sinister