Here's a thought from an old truck mechanic that has never used a gyro, so this is just a guess :
2 brake valves, one for each main wheel brake, connected to the receiver through a gyro.

It could be set up so that if the right main wheel locks causing yaw to right, the gyro reduces air pressure (servo throw) to right main brake valve.

This would not be a true ABS in that a wheel lock on both sides will not be prevented.