[cmax]

From an fantasy perspective for modeling incentives?

An equally powerful/cost effective weapon that left no radiation damage and no burning city afterwards even if there is still only a crater left.

That way you can have mutual destruction without destroying the rest of the world as collateral. It will be a technology replacement.

You will not loose any strategic capability, meaning you can make progress without the "timed-collective-action-threshold-conditional-commitment" thing that is never going to happen with the incentive structure as its now.

There is no incentive for weapons that can destroy the entire world if the entire world is not aligned, only for weapons that can destroy nations.

That said, this line of thinking makes me sick, while at the same time it seems impossible to me without something similar, you have to make them obsolete.