Lateral or Outside the `box thinking is what regulators have tried to move away from in recent times and I agree with this. It is the quality of the procedures that you follow that need to be changed. The MEL should be doing the thinking outside of the box, not the engineer
Then we need to do a lot of work on MEL's because it didn't work this time. Smart engineers and pilots would have prevented this disaster. Systems knowledge by either would have made them realize that the only time the RAT heater works is in the air. Disconnecting the RAT heater does not fix the problem, only the symptom.