This is an interesting idea

Put Chinese soldiers in North Korea, matching the American soldiers in South Korea.  China would have to be desperate to do it.  The U.S. would have to restrain itself from responding in kind.  But the interesting question is "would the North accept it?" Would they tolerate the troops of a foreign power--the foreign power in their immediate neighborhood--to be stationed on their soil?  Would Kim see it as a threat, or a promise?  If the Korean program is really about deterrence, then they might accept it.  If the motivation is not deterrence but attack, they definitely would not.

It would also allow China and the US to call Kim's bluff.  I'd love to see the Korean reaction.

China Should Send 30,000 Troops Into North Korea – Foreign Policy