We did
something like this on our Overdrive bot with the steering(Ackermann steering system). The biggest thing that you have to watch out for is that this will not work as an open-loop system--you HAVE to have feedback from the wheels, or positioning errors will make your robot unsteerable after a few turns. Ideally, you would use servos to handle the turning, but I don't think any of the allowed servos are quite beefy enough to handle that. What we did was hook up a worm motor to the steering system, and then had a potentiometer provide feedback, but the tricky part about this was getting oscillation out of the system.