Yes, I did some more research... although I havent broken my airdrill out of its packaging the big issue with airpower is lack of torque and constancy of speed... so I'll go back to electric motor....

I noticed on eBay a few drill motors, 14.4 and 18v replacements for cordless.. The specs on these look promising 100W, 55Nm torque at 10mm (I need ~50W, ~15Nm) but the spindle speed will be low, maybe 1800rpm, although I read that 14v motor PWM'd at 25v will run faster... maybe I could belt drive it, 2:1 ratio will give 3600 rpm @ 25Nm...

I also came up with a plan to fix mount the motor and belt drive the spindle on a sprung idler so the spindle could traverse the Y plane but the motor remain stationary. Of course the Z motion will require a splined drive shaft so the upper drive pulley remains fixed.... I'm sure there's a catch somewhere, just don't see it yet....