Having shot an automatic 9mm in comp. I don't have any hangups with guns as such. But I would not want them in the cockpit or cabin under any circumstance, undertrained crew members are more likely to shoot a window out(or try to improve their position on the seniorit list)before the threat of highjacking might need to be considered. Well trained airmarshals should be the only armed people, if any, carried on the aircraft.
Perhaps your taser type weapon if any may be more appropriate, this may also be interesting with modern FBW aircraft. I believe some types of modern projectile weapons have been designed to not penetrate the aircraft hull, but no details.
People of ill intent will always find a weapon on the aircraft. They would not have to look past the bar cart on our operations, we still serve beer in stubbies - memory goes back to a bad bar fight.
Don't know the answer but I wouldn't mind my leatherman back in the bag.