If you think about it, it's just two 9v batteries in series with some fancy electronics to guage when the stack is full/empty, and a power regulator to prevent u from sending the full 18v to the servo motor that would probably blow it.
However, since the revvy has no fancy feed neck system to ensure a constant pressure on the ball stack, the most you could hope for is a faster rate of spin. It'll still be an agitating hopper, and there will probably be a speed after which the paddles do more harm than good.
So the answer is yes, u can probably fiddle with the electronics to make it spin faster (Lookup Philip's modification thread for how to increase the operating voltage of the motor) but whether it'll actually feed faster is another matter...