This is a cut-and-paste from a comment discussion I had here with a commenter who was convinced South Korea's labor shortage (aging population) could be solved by expelling foreign migrant workers currently manning South Korea's assembly lines, and replacing them with North Koreans.
I think you're being a little naive if you think that North Koreans will happily be imported to work as South Korea's labor force, and happily swallow, en masse, the second-class treatment DDD workers and tradespeople receive here.
Meanwhile, a group of people who have been raised and educated under such a vastly different ideology than the South, have been regularly instructed on why the South is inferior, and why they should hate or mistrust South Koreans, and whose lack of proper nutrition during childhood have left many physically or mentally stunted... do you really think it'll take any less work and cost integrating them into Korean society, or changing Korean society to accomodate them, than it has to bring South-Asians into South Korea? I don't. Perhaps more... with extra frustration, because while Korean society's dealing with their challenges, both sides will also be dealing with disillusionment: "I thought reunification would be easier than this" where with immigrants, at least everybody on either side already recognizes it won't always be a smooth ride.
Will North Korean workers have the skills and training to fill the needed roles? Or wil NK electricians be lost on any system with technology newer than 1982? Will enough of them have the capacity (poor nutrition = stunted mental capacity) to be trained/retrained? And if there are Indonesian or Filipino electricians with their tradesmen's cards in hand, wanting to immigrate, who are excited enough to come to Korea that they've already completed a survival level Korean course? Why would we turn that guy away in favor of a North Korean who may or may not be able to complete the training?
Finally, have you read much about how North Korean refugees are treated in South Korea? It's kinda shitty. Why do you think that would change if more came... and if enough came to, say, occupy Gwanghwamun square for a protest, what makes you think they wouldn't, and disturb shit in a host of other ways? --and the South wouldn't be able to deport them easily, the way they do with south-asians who demand collective bargaining rights.
The "because we're one blood" anodyne just won't cut it here, and everybody'll get to say that just once to delay actually dealing with the issues, before people get upset at not having their grievances addressed. I'm one blood with my sister, but we used to fight like cats and dogs.