Has anyone tested using a leaf blower to launch the balls? Most people report the balls as being just under 7" so you could feasibly use 7" ductwork as a cannon. Creating a sealed system might be a little more tricky.
As far as feasibility, I don't think you'll get 200mph, but it seems that if you attach a globe motor to a blower you'd get a pretty good amount of air. Maybe the results would be similar to this blower:
http://www.makitatools.com/menu.php?...et&tag=UB181DZ
If anyone could dig up a spec sheet on the motor in this blower we could compare it to the kit motors.