The increased security at the gates is valid - however these are not unsophisticated people, their ops are meticulously planned and researched for months, maybe years ahead, and they would surely find ways to bypass any type of security at the gate if they so wished.
Increasing cockpit door strength is also not the answer. How many flight crew would be able to keep the door locked while FA's and pax were having their throats slit just the other side, not to mention the old "we have a bomb" ruse to lure the crew out - maybe in the hope that these guys weren't planning on taking any buildings out.
The brainwashed Sept 11 twats were armed only with stanley knives. Surely history would be different today if those flights had armed marshalls on board.
With new info (substantiated or not) that there were plans afoot to take out the Rialto - maybe still are, anyone who questions the validity of marshalls in Ozzie skies is at best foolhardy. We are no longer immune to such attacks, and would be considered a soft target.
Additionally it would most certainly increase the travelling publics confidence.
I'm done