For yaw you could have disks mounted on the rotor shafts and break pads mounted on the airframe, when you push a rudder pedal it would lightly rub on one disk or the other. No reversal in autorotation.
That wont work. Since both rotors are coupled the only thing, using your system, will do is slow down both rotor rpm. No yaw whatsopever.
You need to create differentl rotor drag for yaw via different collective or by airbrakes.
I believe it would work. Please tell me the difference between adding drag to the rotor from deploying air brakes (to a rotor that is coupled) and adding drag to a rotor by apply a brake to that rotor.