I hope that a better system is found PDQ because the thought of the chaos that a Sky Marshall can cause by shooting off in an aircraft is not a good one.
When will the gung ho realise that it is only in the movies that the good guy only needs one shot to kill the bad guy. Chances are that the ONE Sky Marshall will be outnumbered by the 'bad guys' and that they will lose the battle, leaving the surviving bad guys to wreak their havoc in a mind set of revenge.
Perhaps if the Govts of UK and USA were serious about solving the problems they might start by trying to resolve the issues which have caused the upsurge in terror, and I don't mean by bombing them to hell and back!