What I find remarkable about the whole event is that it was such a rough and surprising awakening for the aviation community in the Western spheres. There had been numerous pilot suicides/homicides using aircraft in other parts of the world before:
ASN News » List of aircraft accidents caused by pilot suicide
The industry, including the regulators, had completely ignored this risk and put their blinds on.
While at the present level of technology nothing will stop a fully determined flight crew member at the controls from inducing a catastrophic event, all measures must be taken to prevent anyone who has or over time develops such a state of mind of ever being there.
That people with actual mental problems have been there, and do get there, points to a huge cultural and systematic failure of the industry.
There are no easy solutions, and the good ones will cost money; but companies have to assume full responsibility for who they hire and place at the controls of their aircraft, for every flight.
The financial consequences for a company's failure to KNOW beyond doubt who they can trust with responsibility on any flight must be so crippling that companies are forced to either develop deep cultures of care, or disappear; respectively never be allowed to operate.
Such cultures must care for the development and wellbeing of their flight crews, including providing the means to help where necessary and safety nets in case problems cannot be rectified.
It goes without saying that cultures built on financial exploitation of pilots such as P2F or zero hours contracts, competing in a race to the bottom, must not have a future.