Sept 11 has shown that all the usual thoughts on hijackers can now be thrown out the window. Who would have thought anyone would deliberatly crash the aircraft. Before if you all remained calm and followed their demands then most would survive. Now you must assume the worst and use the best form of defence - attack.. .Strong cockpit doors are one answer. CCTV with panic buttons is another giving vital time to act. I think we would need some well thought out mods to prevent auto oxygen deployment if we dump the pressure. Mind you a cabin climb above 6000ft /min would be pretty dabilitating so there's another posibility. . .Like the chute idea though. Into a bombproof container and fill with Halon as a precaution against fire.