UPS's, MOSFETS, PWM and more!

This post will discuss an idea related to the circuitry inside UPS's and a possible application. Now I don't take credit for this idea, I am posting it here to get input on whether you/readers think it is feasible, or have any suggestions on its implementation.This is a picture of the circuit board of a UPS. There are many dead UPS's lying around the ACCRC.
This is a closeup of a bunch of the heatsink, which cools off a group of mosfets wired in parallel, the main current shifter. Each one of these mosfets, an irf3710, is capable of dissipating 50 watts. (according to the irf3710 datasheet) So together, they can supply 1000 watts, easily enough for a powerful motor.

The idea is to take these mosfets, and use them as the basis for a scalable high-wattage motor controller. When I was building a robot (more on that in a later post), the hardest part of the initial hardware design was getting a motor controller circuit which could put out suitable current to drive the motors. Motor controllers are expensive, and the lack of them is the main restricting factor of a lot of the electric vehicle/robot work that goes on here. Anyways, the mosfets would be wired in parallel, allowing for scalability. They would take input from a computer or a microcontroller which puts out PWM, like the arduino board, or the circuit based off a parallel port, as described at http://lukecole.name/parallelport_pwm_driver.php.

Combined with easy pwm circuitry, these mosfet arrays will make it a heck of a lot easier and cheaper to conduct robotic and electric vehicle research. Any questions/suggestions?