And this would stop future hijackings exactly how? I think that a uniformed, somewhat intimidating law enforcement presence is reassuring to the nervous Nellies, but let's not confuse true improvements in security with knee-jerk feel-good wastes of time and money. Furthermore, it's highly doubtful that anyone will ever try that attack technique again.
My suggestions for improving flight security include arming pilots and flight crew, or flying an armed, sworn law enforcement officer. Pilots already have absolute authority over the airplane and its passengers; there is a reason their title is "Captain", and there is no reason corporate policies should forbid them enforcing their authority. Allowing civilians who have a CCW permit to carry aboard would be good too, but that would require federally mandated reciprocity of permits. Deportation of all known illegal aliens and close government supervision of legal resident and non-resident aliens should be done immediately. Careful screening of all carry-on and checked luggage and cargo for biological chemical and radiological warfare agents or explosives should be undertaken immediately.
Silliness like gassing the passengers, banning carry-on luggage, welding cockpit doors shut, and banning private pilots from flying only serve as psychological fixes, with the sole positive effect of showing the government is "doing something."
Let's go back to large flight crews. This lets the pilot send, say, the engineer back into the cabin to handle trouble. Let's recruit cabin stewards from the Marine corps or similar friendly, service-oriented organizations.