But, from a cold, inhumane, and strictly logical perspective, North Korea is a problem that will probably solve itself. Assuming that most of the non-mainstream stuff that I read and hear about it is true (and I'm a little unsettled at even wondering that, let alone specifying "non-mainstream"), North Korea is badly starved for resources.
When your population is starving, when your media singularly carries fictional programming about your state and leaders, when your education is tightly authoritarian, you are less likely to produce the geniuses needed to solve engineering challenges like accurate long-range guidance systems.
Ordinarily, a resource-starved state would devolve into desperation; in North Korea's case, I'm not sure whether to expect that, because the entire state seems to be so uniquely dependent upon the whims and notions of a single individual -- its party leader at the time. If Kim Jong-Un continues to place pride before population, then it's likely that the state will collapse in our lifetimes in a mostly nonviolent way. If, on the other hand, he decides to try to take some kind of action, he'll eventually be forced into a game of poker where everyone at the table knows that he's got the weakest hand. Although he could certainly do a lot of damage on the way out -- mostly to neighboring South Korea and Japan -- he could not destroy the Earth, and he'd be faced with an immediate and deadly counterstrike from more capable nations.
It certainly is a terrible situation for the poor souls born into that country. Still, sometimes the best strategy is to simply wait out your opponent and let him starve to death, and I wouldn't be surprised to find out that this was in fact the Western strategy.