If I were North Korea's dictator (Kim Jung-un) I would exchange my Dictator's hat for that of the crown
Have you ever fantasized about being a dictator? Me neither.
However, if I were Kim Jung-un, I would seriously consider following in the foot steps of England. He could entrust the North Korean estate to the Republic of Korea in exchange for a x amount of funding for the royal family.
In such a move, he would go from bad guy, to royalty of both North and South Korea. Such an act would protect himself and relations from assassinations, guarantee a place in history for his children, his children's children and s on. All while maintaining the lifestyle to which he is accustomed, the lifestyle of royalty.
Such an act would allow the South to reintegrate the northern population in stages, perhaps allowing x number to move south each year, while building infrastructure and educating the northern population for full integration... to avoid economic depression, this would take 20 to 30 years. Any sudden change would see the south under huge economic pressures as the Republic of Korea would find itself inundated with what are essentially refugees, a good percentage of which have spent their entire lives in prison cities-- northern prisons are that big.
Finally, such a move would minimize the impact and rebellion against reunification among Kim Jung-un supporters. Though a percentage would remain loyal to the norther ideology, that percentage would be significantly smaller than were Kim Jung-un to be displaced, imprisoned, exiled or executed.
Obviously, there would be downsides to such a move. Such an act might require that he acquiesce to something akin to house arrest, but leave other relations such as children and perhaps his sister, free to live their lives. Certainly one upside to such a deal would be protection from the threat of assassination.