Fail safe BEC?

My CC BEC just decided to stop regulating voltage and sent full battery voltage to all my components. So my new spektrum Rx, hitec servo, and cooling fan are fried.
Of course, CC will not cover anything beyond the BEC.

Anyone know how to add an additional simple circuit (like a zener diode/resistor shunt) that can clamp the voltage to prevent this from happening again? 300$ is now toast due to a 20$ little BEC. Seems to me BEC's should be designed to fail open, not closed.