ASIC speed grows in bursts. Eventually one of the bursts will allow to rewrite the whole blockchain from the genesis within a day. I wouldn't say that PoW is that secure as you think.
That would be a 51% attack.
pos is much more secure than pow. you can't attack pos without notice or real world feedback but you can on pow.
on pow an evil entity could easily aggregate +50% silent, in the dark, without any chance to prevent this.
even without any new fancy, more powerfull asic design, this attack could occur anytime and compared to a pos
with a similar macap it would also be cheap, very cheap.
to follow your crude 'pico-probabillity-attack-vectors' on pos, here is a crude pow one for you. just imagine that
for whatever reason, the power-lines to the three chinese mining-warehouses randomly gets broken. i guess in this
case the attack would be much cheaper, perhaps close to free compared to pos and as said, just out of the dark
without any chance or sign to prevent it. this is impossible with pos.
however, whatever possible attack vector you are constructing, it boils down to this. if you try to find a solution to fix users,
having the goal to destroy their own stuff serving them (your gen key example) you will fail, no matter how fancy your math is.
there is no solution for lunatic or planed selfdestroying behaviour simple because even if it would, it has no value because the
target and reason for this solution dissapears.