[Al Skierkiewicz]

Eli,
I have to ask how big you are planning to make this robot? The CIM motors are obviously capable of driving a full size 150 lb robot. I suspect what you want is something much smaller and not nearly as fast. While not a big fan of FTC motors, they do the job on that size robot every year and the hardware for driving them is available. Arduino support is also available on the net.
I seriously doubt that a CIM driven CNC would give you the accuracy needed or do a better job than stepper motors. The brush spacing won't give you the accuracy needed for precision machining.