One of the main issues is that the passenger doesn’t have to even get up. They would have to move the door control handle to about the 90 degree position, the door will do the rest.
Apart from the obvious safety issues of having a door open inflight, the main “aircraft” safety issue is the deployment of the slide. If that thing gets wrapped round the tail you’re in a whole world of pain.
looking at what has happened here the aircraft is flyable with the door open, so at least that’s something.
I think having the cabin over pressurised to keep the door shut is a bad idea. If something were to happen on landing the aircraft would go up like a bomb.
The idea of a lock is something, but what if it doesn’t unlock in an emergency?
Maybe lowering the PSI in the power assist bottle would work, so the door cannot open into the slipstream?