The Confucian idea of unquestioning obedience towards those of higher social and political rank is one that is simply foreign to us, and indeed is very difficult for the vast majority of westerners to understand. I can think of no scenario that would be able to erase this very basic and deeply ingrained social structure that is so firmly entrenched in North Korea.
There is a fascinating book I recently read call Nothing To Envy, by Barbara Demick. She chronicles the lives of several North Korean defectors, and interviews them extensively, spending several years gathering their stories. One very common part of the narrative of the defectors is that they actually miss living in North Korea: they felt a deep connection to the Kim regime and truly believed that Kim Il-sung is God: a true deity, here on earth in the flesh to provide for the people of North Korea. Before the famine in the 90’s, the North Korean government provided everything for the populace: food, shelter, clothing, heat, employment. They received government vouchers for everything they needed
Defectors often complain about how alien the capitalist society of South Korea is. Learning how to pay bills, paying for their own food, understanding the consequences of frivolous spending (In North Korea everything was provided, so budgeting was never an issue)…all this adds up to group of people that, frankly, liked it the old way.
North Korea has a population of ~25MM people, the vast majority of whom literally worship the Kims. By any rational objective standards the average North Korean lives a life of utter poverty in a draconian, totalitarian state… but they don’t see it that way. It’s the only thing they know, and will fight to death to protect the Kims and their regime.
It’s also important to note that North Korea is stable. Despite the crazy pronouncements and other wacky behaviors from little Kim, the regime remains happily in place. It’s survived the fall of the Soviet Union, China cutting off trade, and massive sanctions. Clinton almost went to war with them, and Bush the lesser bitched about them often. But today North Korea remains unchanged and unchallenged. While the people of North Korea suffered mightily, the government itself is stable.
So to actually answer the OP? The only thing I can think that might work by a Western power would be a Marshall Plan-like humanitarian effort combined with a massive denazification-style education campaign put in place immediately after the assassination of Kim, his cabinet, and the military brass. But that’s a blue-sky guess, as I’m confident that absolutely nothing will actually topple the regime short of massive internal insurrection. And considering how deeply Confucianism and worship of the Kims is entrenched in their society… that just isn’t going to happen.
And has been already pointed out numerous times, North Korea could never win a shooting war with the US and South Korea. However, since they have enough artillery to reduce Seoul to ashes and are apparently just waiting for an excuse to fire it, it seems like the current policy of just ignoring them and allowing them to exist in their little cocoon is working fine, at least as far as the international community is concerned.