The FA in deck policy (when a pilot leaves) means that in addition to pilot and FO now any flight crew member can lock the cockpit if he is fit enough to knock out the seated pilot. That might cause more harm than it's trying to prevent.
To my (lack) of knowledge flight crew recruitment does not take the degree of scrutiny that pilot selection takes.
It's not easy to prevent a crash when the pilot wants to crash. Hence i tend to concur with Lufthansa CEO. As sad as it might sound.