But now, South Korea seems to have realized there is something worse than South Korea absorbing North Korea--China absorbing North Korea--via investments that lead to invervention--and taking the place of the North Koreans on the DMZ:
But what South Korea really fears is a North Korean agreement that would allow massive Chinese investment in North Korea. The Chinese investments would be safe, because the Chinese would not hesitate to send in troops to deal with any North Korean misbehavior. Large scale Chinese investment in the north would enable China to eventually take control of North Korea, and annex it. Many starving North Koreans would prefer to be prosperous Chinese, while North Koreans who opposed such an arrangement would be killed. China is still a communist police state, and knows how to act like one. This Chinese takeover would solve China's problem with the growing economic decline and political instability in the north. The South Koreans are horrified at the thought, although China has taken control of the north before (in the distant past). China would apparently prefer not to have control of North Korea, but the growing problems there will not go away.
Yeah, right now China would prefer not to occupy North Korea because of the cost. But like South Korea's realization, China will understand that having South Korea on the borde of Manchuria is worse than absorbing North Korea.
If China and South Korea no longer consider occupying North Korea the worst case scenario, how do we prevent a collapse from leading to war?
I say, partition the damn place.