If your aircraft is so poorly and dangerously equipped in so much that it has a lockable cockpit door but no method of entry from outside, then you can have two choices. One is never to leave. The other is to always replace the person who leaves with another whose sole function is that of door opener. And that is to over-come a dreadful lack of redundancy in the door design. There will be no other benefits (other than a possible improvement in your captain's morale if it's you being replaced) because an average CC member will not be able to prevent a take-over of an aircraft.
And I think if you read my previous post you'll find that the reference 'muppet' referred to people not normally found in flight decks. I was suggesting that they may placed there by pathetic, ill-considered, knee jerk legislation in the future.