Awesome concept. I saw this in my daily email feed and registered just to post!!! I think you are ok to something and offered something that came to my mind- they may spark your innovation-

How does a concrete vibrator work? Is that too much vibration?

What if a hammer drill was added at a lower speed?

What about an impact wrench with its hammering capabilities?

I agree a small 110v motor with a rheostat to control speed would be awesome!

Kyle