Cabin crew in the flight deck, no thank you.
There are only two ways to prevent another GW or MH370,
No 1, remotely controlled aircraft, ie, drones, no pilots, it will come but not for quite a few yeas yet.
No 2, Flight Engineers, it was a massive mistake to remove Flight Engineers, you can have an unlicensed/untrained stewardess or hormonal steward who do not have aircrew training or medicals and do not have a clue what is happening in the F/D, any pilot can wind down the altitude, turn on to a heading, reprogram the FMS or even switch off all engines and cabin crew would not have a clue, just carry on chatting, or a Flight Engineer, who has years of training, knows everything that is happening in the F/D, knows what every c/b does and can correct altitude loss, reset to the correct HDG, can make sure the FMS takes the aircraft to the correct waypoint, he can even restart the engines.
A cheap get out by the authorities.
CC or F/E, you chose.