G'day AC,
Reminds me of the draconian knee-jerk reaction from the US Army when one of their OH-58 was stolen by a scrubbed stud and landed at the governors house, to prove that he could fly (as relayed to me).
Keys were fitted to the A/C to isolate the ignition circuit. End result is a massive dick around with lost keys, etc.
How many aircraft are stolen anyway? Surely if the thief can control a helicopter well enough to 'do damage with it', then suicidal or not then they can get around the security. Who doesn't know where to find the door keys for a parked JetRanger?
The only answer is that pilots should hide their aircaft after each flight, as keys are too fiddly and easy to lose.
Gibbo