[JesseK]

The major problem I see with a worm gear on the main drive wheel is that for the wheels to "lock" and not move, inwards or outwards pressure is directly put onto the motor shaft. There are ways around it (shaft collars is the first thing that comes to mind), but it definitely could wear a motor down over the course of the 30-50 matches your robot has a potential to compete in if it's not accounted for.

Other than that it's a very nice simple design, especially for a defense+ramp robot this year.