youdontknowme Cooldown and nuclear option are just two different levels of safeword. Unless you do not trust yourself to not abuse your safeword (and thus need the threat of a ruined keyholding relationship to prevent you from using it too eagerly), a simple safeword for "unlock immediately and talk about the future of the arrangement" will do.
I prefer the safeword option, but it seems that cooldown is often used in key holding dynamics, so it’s worth to mention it
@alyssame cooldown the time between you asking to get out and the belt effectively being removed. It is used to prevent hasted decisions, but it is not substitute of a nuclear option, that is something like “free me or I will call the police”