How about upgrading the controller for free (well almost) You still have to buy the hardware, but I'm giving away the software for now. It is running very successfully on 4 machines at this time with full 4 axis profiling capability. Will digest millions of lines of G-code with deep look ahead for smooth motion.
Upgrading a MultiCam should be pretty easy, the ones I have worked with are all step & direction with the loop closed at the servo drive rather than the controller. I have also seen MultiCam machines with open loop steppers. Either way it should be pretty easy, very basic machines.