Perhaps go backwards to a large red "remove before flight" flag attached to a "key" that operates the gust locks externally Then that same "key" could be designed to release throttle-locks IE it must be inserted and locked in place before throttles could be moved from closed. ?....yep, a ballache, but it would save stupid from itself. )(apart from the danger that some smartass would use a duplicate "key" to unlock the throttles whilst the controls were still locked.
make it idiot-proof, you'll breed a better class of idiot.
These people were killed by complacency.