Your way would be a rostering nightmare. If there Must be a half-bar CA on every flight, in the front galley, what happens if they take ill and there is no qualified standby? Do you cancel the flight?
Then think about "How could a person with ill intent USE this system?"
jaytee
Surely the same argument would go for a Cabin Crew manager/ess or senior Cabin crew and rostering? if they are not available do you let the aircraft go with newbies?
who ever is allowed to enter the flight deck to diminish the likelihood of another Lubitz must surely be trained for that role and know how to unlock the door or handle different situations with a difficult or potentially dangerous flight crew member.
He/ She will be alone with that potentially dangerous flight crew member so probably not the best idea to send up a 22 year old girl who has been one month on the job and doesn't have a clue what she is looking at or dealing with?
Have you considered the possibility of a planted terrorist taking such a job ? at least this way you will only use CC with three years on the Airline which itself will reduce that possibility! Nothing that is done will make a future Lubitz impossible only less likely.
There are already private reporting systems in place where a pilot can report a safety concern without making it official and keeping a degree of anonymity. Part of the reason that lubitz got through the net was that no body noticed anything wrong with the guy. Colleagues and friends are best placed to notice and report concerns over any pilot so maybe such a site could be accessible to pilots, friends or relatives to make their concerns known whether justified or not?