Your point is a good one that my system would only protect us against threats we know about and it doesn't protect us against stuff we haven't heard of yet. It just raises the question though of how to protect against stuff we haven't thought of.
And there's a problem - airport security seems to be geared towards what normal people like us might buy into. It goes back to my post earlier - our planners in this area are fighting yesterday's war.
Within a few months after 9/11, a few defense security guys were interviewed on TV (pbs? nightline? can't recall). One of them was so angry he couldn't see straight. He detailed some 6 or so threats that in his opinion common sense dictated should be stopped, so as to make our security not obviously laughable. And to hear him talk, they all sounded like common sense - I'd already spotted 3 of them myself. The interviewer asked if he knew, why was he detailing his interview instead of telling someone - answer: he'd already told everyone in the establish and was dismissed over political reasons and - get this - because he might people ideas. I wrote down the list and it took them several months before heeding his warnings.
In one of our cities, TSA has a big board of the weapons they've confiscated since 9/11 using their new security methods. There were ugly knives and pistols of every kind. All stuff the old scanners caught magnetically.
As big a threat as terrorist - idiots and the mentally deranged.
In the decade before 9/11, we lost a domestic flight because a loony toon smuggled a .38 on to a plane and shot the flight crew. We beefed up security and scanners for that - as well we should have, that should've been caught by existing scanners.
But it didn't kill thousands of people, so the media and congress let it slide.
I'd say a few things we do to improve for tomorrow's threat: 1) put the DoD and DOE in the loop - there are people who have the resources and organizational experience to think of tomorrow war and tomorrow's security needs; de-politicize airport security, and make it a matter of defense security, not a new branch of law enforcement; 2) synchronize our passenger defense and airport security with our counterparts in foreign countries.
The thing is it's virtually impossible to be fully protected against people who are willing to kill themselves to achieve their goals. Giving up our rights to try to achieve an unachievable goal is pointless. Yet no one wants to come out and admit that we're fighting windmills here in a lot of ways. We can only go so far.
Airport security is very much like our defense establishment was at the fall of the Berlin wall.
It had already occurred to the defense community back then that we were heavy with force-on-force capability for conflict with a like foe - but we were unprepared for guerrilla warfare. We were hoping we were wrong and that the next threat wouldn't be small, agile and lower-tech. We learned quickly that that wish wasn't saving us, and a lot of work went into re-thinking our planning and training for the military.
TSA isn't thinking in those terms yet - they're thinking in terms of show and big budget, not in terms of small foe effectiveness.
When I followed the matter of congress turning away in modesty while TSA demonstrated how to grope a woman's boobs, and then turned around and said carry on - I was reminded of every time Westmoreland and his kind put one over on LBJ.
When civilian authority turns a blind eye, you'll get the foxes guarding the henhouse, every single time.
Here's a solution in counterpoint to your hypothetical. Drop the high tech. Go back to magnetic scanners and chemical sniffers; raise the price of every ticket by 1/2, use the surplus to put a uniformed judo expert with a machine gun or taser in each aisle seat.
Here's the problem with that plan - it's utopian and designed by a non-expert.
