So, which airline will be the first to require a member of CC to be in the flight deck whilst one of the pilots attends to a call of nature ?
All this does is shift the problem from pilots with poor intentions to CC. A CC member, locked in the Flt Deck almost has an easier task than a sole pilot to create mischief - especially considering the equipment in the Flt Deck.
If the person's intent is terrorism related i.e. a sleeper, decide which is easier to plant: a pilot with an intensive six figure training process to go through, or a few week CC induction course?
Currently, a CC member would be pushed to rely on getting cockpit access with only 1 pilot present.