How to setup Ground steering not sending PMW when disarmed?

On the simulator, I set the MOT_SAFE_DISARM to 1 and expected the ground steering to receive no PMW, but it still gets the trim 1500 value which will keep the rudder in the center. The project is for my real sailboat so I need to disengage ground steering when I want to hand steer for a while but without shutting down the pixhawk. Even the servo will mechanically be disengaged from the steering wheel when hand steering, the rudder shaft sensor (potentiometer) will still move, so the servo will free run to get at the 1500μs.
Is it ok to insert an on-off switch on the servo+ wire to cut the power fast? Otherwise, I will have to enter the ground station and disable the ground steering channel every time I want to hand steer, which is time-consuming or shut down completely the pixhawk.
Thanks for any feedback!