The wheels spin as a result of friction with the ground and are independent of the thrust being provided by the engines. A conveyor can't stop the forward motion of the plane.

The hypothetical is flawed. The conveyor can't stop a planes forward motion. Speeding it up only slows it down by the amount of friction that is being created between the wheels, bearings and ground.

The only way it works would be to in some way increase friction to counter thrust. Only then would forward motion be stopped.