Little late of a reply, but I have considered outrunner motors.. One huge problem is that they cannot get rid of heat when they are at rest.. Airplanes give access to tremendous amounts of airflow, a CNC, however...
Another problem is their tiny 2mm-3mm shafts. Finally, the fact that the outer-rotor spins creates problems with vibrations. The only good way is to use inner rotor brushless motors, which are hard to find with a large enough shaft diameter. You could use a frameless brushless motor from Danaher Motion, but they're damn expensive.
Steve