They have had them on gassers for a long time. Not the point of being able to reverse the plane in flight though. Just to make them more efficient.

Glow conversions are going to take a heck of a lot of engineering to do.

The reason why it's so easy with Electrics is that the main shaft can move through the motor. On gas/glow the shaft is connected to a crank inside the motor.

Might as well just get a heli.