In all fairness, we would be lucky to turn North Korea into an overtly occupied satellite. One of the Immutable Laws of FR, 'North Korea is a puppet, China pulls the strings', is dead wrong. The DPRK is a loose and deadly cannon. The North Korean people may fare no better than Tibet under Chinese rule, but that's a lot better than what they have now. It would also be safer for the neighbors, and ultimately, safer for us.
The article misses the mark about the PLA needing to make it to the DMZ before a DPRK attack on the South. They don't need to do that at all, they only make it to the DMZ before we can break their lines and push north into Pyongyang.
China wouldn't be able to hold onto them for long, anyway. Pressure from South Korea and Japan would threaten their economic prosperity, which is far more important to the Chinese than holding on to less than worthess real estate. They will want to grab it, but to give it back under their own terms.
What China doesn't want is a successful U.S. lead war that brings us to the Yalu, possibly for a long, long time. If they were able to sieze North Korea, and make it's return dependent upon U.S. forces leaving South Korea, then they'd have some real leverage. Many South Koreans would leap at the chance to get rid of us. With the threat from the DPRK gone, we'd have no reason to warrant such a large presence.