The learning part is ok, but... if you found a controller that work just like a servo, and you know how to control a servo then using the controller is redundant.

By the way, the controller can't SUPPLY 50A, it can CONTROL a load up to 50A. The current is supplied by the power unit that you are using (in your case I assume that you'll use some kind of batteries, AA like), that won't supply that much since the robot dimensions are very strict by the rules of the contest.

Another thing, you are entering a competition, with a deadline, so you should try first a basic and simple design so you can participate in the competition. If your project is finished before the deadline then you can add some fancy parts to improve your learning experience.

A trick when designing or building a project is to leave some good ideas aside. When you start to see your design working almost imediatelly you see different ways to improve it, or to add new features. If you start wandering too much among these good ideas your basic project isn't finished.