In North Korea's case I'd argue that a "controlled collapse" is better than overt military action and causing the regime to collapse really shouldn't be that hard, since it's just a matter of getting China to be willing to actually enforce most existing sanctions and maybe add one or two more.
No chance of that happening in the near future though, although the North Korean population isn't as isolated as it's always been and the regime has nowhere near the total control it used to have. Furthermore there's no way of knowing when a seemingly random act of desperation, like street vendor lighting himself on fire, will resonate with society at large and set off mass unrest.
Good points.
I think that most of the foreign policy with North Korea seems to be revolving around waiting or hoping for a controlled collapse.