What I would hope to see is perhaps a two piece item that is a completely non standard calibre. The round should be a low velocity high impact type for instant incapacitation. It should be purpouse built for utility cheapness and designed in a manner that would make it unsuitable for use oustide the limited scope of it's anticipated area of use ie the cockpit. One section which is small and convenient for carriage can be issued to the pilot. The other part of the weapon is left on the flightdeck. You reach the flight deck you assemble the weapon. End of flight you retrieve your section.
Flare pistols are routinely carried in life rafts, this weapon is no more, or less lethal. Some flare pistols are in fact made principaly of plastic and fire a small cartridge similar to that of a small shotgun shell, and before we leap off down that tangent I am not advocating using a flare to ignite would be hijackers though the thought is a satisfying one.
We are not looking for the 'Peacemaker' or turning flight deck crews into 'Dirty Harry's'.
There exists a new hazard and with a reasonable ammount of thought, comparitively little money and some common sense, a reaonable solution should not be impossible to achieve that does not create a bigger hazard or involve huge ammounts of training, money, emotion and red tape