Prevention is the best cure!
On any jetliner, no unauthorized person should get access to the flightdeck. This means simply that previous methods of dealing with hijackers must be discarded. The cabin crew will have to learn how to use all available means to keep the bad guys out of the cockpit. This includes use of PA as well as focusing their training on possible onboard equipment that might serve as an effective weapon.
In the meanwhile, leave the flying to the guys up front.