Post made for three hours last night (9pm-12am EST) have been deleted. This was necessary due to some problems with server maintenance. Anyone who had problems logging into their account during this time should be fine now.
Does "keeping it Communist" allow for introducing Deng-style reforms, and opening itself up economically and to some extent culturally to the west, with a concurrent reduction in hostile rhetoric? Because, IF you could find a way to make that happen(and it might mean jettisoning the OTL ruling family), that would probably lead to the outcome you want.
Another thing might be for Beijing to announce to the world that they would regard an attack on the DPRK as an attack on China, and would defend themselves accordingly, up to and including the use of their nuclear arsenal. If North Korea itself trusts this promise, it might cool the perceived urgency for them to develop nukes of their own, which would make them seem less threatening to the world.
In tandem with either or both the above scenarios, it might also help if the ROK somehow remained mired in right-wing dictatorships, especially of the calibre of Chun Doo Hwan. So a lot of the world would think "Well, not much to choose from anyway on the peninsula", and North Korea looks, if not outright good, at least not quite as bad, relatively speaking.
This might come as surprising for some people, but in the aftermath of the Korean War, as North Korea was rebuilding, it was acutally more prosperous than the South, which at the time, had become a bonfire of political disorder with coup after coup. North Korea's prosperity was brought crashing down by the Soviet Union's collapse, which led to the Arduous March famine, and at the same time, South Korea had transitioned to a liberal democracy. South Korea was opening up, while North Korea retreated inwards.
So, if you find some way to keep the Soviet Union around and keep South Korea in political limbo, then North Korea could be seen as the better option.
Thirty years ago, North and South Korea were more alike than different. But a vast gulf has opened between the two countries since South Korea last hosted the Olympics.
Another way is for Kim il-Sung to die at the Battle of Pochonbo, which in North Korean historiography, is seen as one of Kim's greatest triumphs against the Japanese occupation of Korea. With Kim dead, North Korea could resemble more of a traditional Communist state and avoid the personality cult which has pretty much made North Korea a joke to the rest of the world.