If I was to design a reunification strategy, I'd probably start with limited emigration/immigration into and out of the country. Open up trade as much as possible (except for defense). Start allowing the people of the North to build up capital, and have a reason for staying. When the country is more stable, then I'd open up immigration more widely.

I'd also ensure basic human rights are currently being addressed. I don't have a solution for past violations, that's a tough issue.

Basically, I'd go with the China model.