If a reverse switch, relay, or contactor was installed between the motor and controller and used for braking then the controller would be the first part burn out, and chances are that it would burn out immediately. Due to the this the motor would probably be okay since the controller would stop working before it had a chance to become damaged.
What is needed is a controller with electronic braking so the braking force is not in reverse. We are working with a manufacturer right now to have controllers for brushed motors which have an electronic brake custom made for us. As soon as we have these controllers available I will reply again to let you know.