John, how are you going to garrentee that you don't lose position due to slippage? This style of motion would seem to be good for several applications, however I'm not convinced that it applies to well to CNC. Most people who are doing something similar are using drive belts which are "cogged" so as to not lose position.
If going to a long belt isn't apealing.. the next option is a rack & pinion setup.
My two cents..