I think there's a slight misscommunication here (probably on my part).
The instability in NK isn't only from a change in attitude, though that HAS been significant in recent years. The instability comes from the fact that it's getting harder and harder to ignore the *starving population* and *rapidly failing "industry"*. Even the strongest True Believer in the Kim family regime has to be doing an increasinly absurd amount of justification. The fact that some (still VERY small, but growing) portion of the population has started to look outside that carefully controlled box is a byproduct of this decay. There are many parts of NK that are really only holding together by the thinest of threads, and that imbalance is harder to support when you run out of natural resources and productiivty to pillage.
Hence the problem for China: if NK went full rebellion, tthat would sugest there's a certain critical mass of people within NK that could handle stuff like rebuilding their infrastructure, at least in principle. After the dust settles, go in with some UN people to offer a bit of financial or industrial help while they bootstarp. As bad as revolutions are, that situation at least has a "reasonable" chance at a stable, not-horribly-expensive-for-China outcome.
Unfortunately, as you note, there ISN'T enough support for a traditional rebellion. It's a big change in attitude for NK, but you can't erase that much indoctroination overnight. They likely will need a nation's worht of "deprogrammers"/exit-councelers or somesuch, which is *not* something China (or anybody) really wants to be suck providing.