Multilateral disarmament treaties similar to the SALT treaties with the USSR? Maybe at the UN level rather than simply administered by individual countries?
I'm not disagreeing with that in principle, but practically speaking North Korea is not going to cooperate and I doubt there's enough trust between the other nuclear powers for a full disarmament treaty. The second best, and more realistic, option is to make everything very public and transparent... which is really just MAD, but with smaller arsenals.
That sounds like a good way to get a major city nuked.
We already have enough conventional weapons to bomb NK back into the Stone Age, should it be necessary. I'm not sure which other countries you're referring to that are not trustworthy diplomatically, but, IIRC, there are only a handful who have nuclear capability (China, Russia, Israel?, Iran?), and those can be dealt with using existing satellite monitoring capabilities to detect nuclear buildup, and treaty monitoring.
I would much rather reduce arsenals to zero or near zero levels than risk having Jericho happen in my backyard.
