No fly = War.
At this point, sneezing towards the DMZ would trigger a war, according to Lil' Kim.
I believe that the reaction of the North would be immediate and violent. They would correctly conclude that incremental loss of control of the air would completely undermine their warmaking capabilities. Finding themselves in a classic "use it or lose it" situation, the North would opt to "use it" against Seoul.
This is not to say that I would oppose a "no-fly" zone. I only caution that it must not be imposed without a full appreciation of the consequences, and mobilization of all required resources to deal with those consequences.
Yup, might as well impose a no dictator zone.
bump
It's called calling their bet. Either they fold their hand, or back-up their continual war bluster with real war, in which case they get destroyed. I like it as an eventual step if we're ever going to resolve this situation.