Hi watergeorg. That is a good idea, but I dont think it will work. The problem is that a plotter only has to carry a pen, and there is not much stopping the pen from moving. You will also notice that the frame on a plotter is quite small, as the pen is not very heavy. If you put even a small dremil on it, it will bow and start to move. Also, i dont think the motors will have the power to move the waight of the dremil.
in answer to slowing doen the rate of movment of the pen, you can do it with software, the rates are programmed intot he conntrol hardware of the plotter. The computer only tells the plotter where to go, not how fast to get there.