Much more difficult to secure against accidental ejection though.

It is indeed terrible to crash accidentally yourself to death when you want to crush yourself to death on purpose.

I was thinking of the cleanup crews. People are always very inconsiderate of those when killing themselves :-/ Ever saw the mess it makes when somebody jumps in front of a train?

Negative G is much more uncomfortable than positive G.

not necessarily, some would black out pretty quickly. Lateral Gs are the by far most uncomfortable G forces (and other non vertical i suppose)

You will never black out from negative G. You will RED out as blood rushes into your eyes. The reason you black out from positive G is that your blood pools in your legs and feet, starving the brain. Negative G is more uncomfortable because our organs are not designed for it, as it isn't encountered in nature.