STC, it's already been said on here that arming the flight deck crew won't cure everything. However, we're getting armoured flight decks anyway: at the very least these should slow down a hijacker long enough for one pilot to draw his weapon, unstrap, turn around, and be ready for him: then we're back into the "fatal funnel" described above.
It's a last resort; as with all last resorts it is hopefully never going to arise. As I've said before: I don't want to carry a gun to work- but I think it would be safer for me, the rest of the crew and our pax if I do.