In all the recent cases someone has identified the pilot as needing to be tested. It has been obvious that something was wrong and subsequent testing has or has not shown a high blood alcohol level. In all cases the pilot has been prevented from flying. So it is unclear what the lack of workforce morale, the cost, the legislation, and numerous other issues involved in mandatory testing would improve.
I would rather see more training for flight crew, cabin crew and others to ensure that they do not drink inappropriately in the first place, and are more aware of the need to challenge each other.
I am less enthusiastic of 'training' security staff as I suspect it will cause more harm than good.