In this thread https://vexforum.com/t/answered-question-regarding-robot-design/29644/1, it was ruled that a robot could have two distinct forms so long as it didn’t go far enough to be considered two robots.
<R1> Only one (1) robot will be allowed to compete per team in the VEX Robotics Competition. Though it is expected that teams will make changes to their robot at the competition, a team is limited to only one (1) robot. As such, a VEX robot, for the purposes of the VEX Robotics Competition, has the following subsystems:
Subsystem 1: Mobile robotic base including wheels, tracks, legs, or any other mechanism that allows the robot to navigate the majority of the flat playing field surface. For a stationary robot, the robotic base without wheels would be considered Subsystem 1.
Subsystem 2: Power and control system that includes a VEX legal battery, a VEX control system, and associated motors for the mobile robotic base.
Subsystem 3: Additional mechanisms (and associated motors) that allow manipulation of game objects or navigation of field obstacles.
Given the above definitions, a minimum robot for use in any VEX Robotics Competition event (including skills challenges) must consist of 1 and 2 above. Thus if you are swapping out an entire subsystem of either item 1 or 2, you have now created a second robot
Based on these definitions and stipulations, would it be legal for one form of a robot to have a motorized drive train, and the other to add on several more wheels? These wheels could either be controlled by separate motors, the same motors as the original wheels, or no motors at all.