There are already FAMs in the main cabin.
If you believe that is always the case, worldwide, you have been misinformed.
Just remove cockpit doors altogether so that a terrorist (whoever that might be) cannot lock himself into the cockpit, and we are all set
Yep, Mr Bin Laden's mates would be all set...........
I think Flight training for FAMs should be no problem
I'd suggest firearms training for suitably screened flightcrew might be even less of a problem.