Here’s a crazy idea, you look at the personal life of the crew

Here's an even crazier fact - it's not always that obvious.

And a "damn good guess" is still a guess.

Or you just look at the thousands of non pilots who committed suicide and then use that data

Non pilots tend to commit suicide alone. They don't take hundreds of innocent people with them, so they're an entirely different group in an entirely different scenario under entirely different pressures. The data is not directly transferable.

and then costs are going to go up 100x because it’s now “aviation grade” materials

This is an issue that can be solved by removing bullshit steps to certify an item that doesn't need to be any different to one used in other applications. You don't need an "aviation grade" camera. And there are plenty of planes with cameras in certain areas (infernally and externally) already. Part of the procurement system being flawed (especially in the US) isn't a reason not to make changes.

It's a reason to fix the flawed system.

Then you need to pull a plane off the line and

This is why I said it could be installed on new aircraft or alongside already scheduled upgrades, when the plane would be out of use anyway.

Then parts are going to break and need replaced,

Because what's essentially a glorified dashcam is known to break frequently. Oh wait, no it's not

So yes it will certainly get into the billions of dollars across the industry.

Sure in an exceptionally poorly managed worst case scenario like you've dreamt up. Same as any other modification.

However it doesn't need to cost nearly that much.

And for zero increase in safety.

I quite literally highlighted that the increase in safety is proving who caused an incident so you can be certain - and then know what to look out for to avoid repeating it. Rather than guessing based on factors that may or may not actually point the finger in the right direction?

You can pretend not to understand, but the benefit is obvious.