I doubt the Chinese would want to overnight take on responsibility for the basket case that is North Korea, but if they did it seems this would be one of the least bad options for the United States to resolve the nuclear issue:
A longtime editor of a magazine that specializes in global power politics recently put forth a scenario where China would stage a takeover of North Korea, giving Washington and the rest of the world a nuclear weapons-free Korean Peninsula.
Bill Emmott, the former editor-in-chief of The Economist magazine, said such a move by China would not only gain Beijing a solid foothold on the Korean Peninsula, but also the opportunity to strengthen its own geopolitical position, enhance its global power status, perhaps even the ability to claim the reputation of a peacemaker.
That is the “least bad military option” vis a vis North Korea, Emmott said, in that it would avoid subjecting U.S. allies in Asia, including South Korea and Japan, to North Korea’s retaliation that could potentially devastate large parts of South Korea.
China’s takeover of North Korea, as Emmott sees it, would put North Korea “where the country’s post-Korean War history suggests it belongs: under a Chinese nuclear umbrella, benefiting from a credible security guarantee.”
He also said he sees incentives for North Koreans to go along with the plan: “Whereas a nuclear exchange with the U.S. would mean devastation, submission to China would promise survival, and presumably a degree of continued autonomy.”
Emmott said this strategy could win over a majority of North Korea’s military, “except those closest to Kim.” [VOA News]
You can read more at the link, but considering the importance of race based nationalism in North Korea getting the military to go along with this idea I think would be a very tough sell.