Just give them to Kim and watch them experience infinite annihilationKoreans really think highly of themselves don't they?
In reality China won't even bother fighting them, if they misbehave China can just blow up all their power plants with drones and keep them eternally locked in 18th century as a side quest.
Tbh once China initiates the Taiwan defense and colony recapture war against US, will China actually give the southern half to NK? Or keep it themselves under a mandate until Kim's government is "mature" enough to recieve control.
Because it's hard to imagine NK which is generally not well developed and even poorly electrified can shoulder the administrative burden of integrating SK.