One place I could see changing things in North Korea is its relationship with China.
I’m sure the lack of knowledge I show in this post will make me look ignorant, but I’ll share anyway. Most of what I know about relations between China and North Korea come from three sites

• The Council on Foreign Relations’ report The China-North Korea Relationship
• The Council on Foreign Relations’ report The Six-Party Talks on North Korea’s Nuclear Program
• Wikipedia’s article People’s Republic of China–North Korea relations

The first CFR report seems to cover the main topics well. I’ll distill what seem the most salient points for strategy.
The main point is that China has the largest border with North Korea and it is relatively unguarded. North Korean leadership could not survive without Chinese aid.
China fought and sacrificed a lot in the Korean War and continues to support North Korea with resources like oil and diplomacy like backing it in the U.N. and elsewhere. North Korea gets a lot from China.
What China gets from North Korea is not as obvious. It gets access to North Korean natural resources and probably cheap labor, but I think those benefits are minimal. I think the two biggest things China gets are

• A buffer against the United States military presence in South Korea
• Stability against who knows who or what might replace the government of North Korea

Note that North Korean leadership controls both of these benefits, not China.
That China has supported North Korea for so long suggests these reasons are significant. Other issues include history and ideological agreement, though I expect both of those are minor and decreasing. I expect the importance of the buffer from the United States military is decreasing over time as the U.S. and China’s relations improve. Compared to a generation or two ago, they are much closer.
Still, there is a stability now that would be hard to break up and that North Korea can maintain, giving it power. As long as North Korea appears belligerent and unpredictable, South Korea will fear invasion and want the U.S. to keep protecting it. As long as the U.S. remains in South Korea, China will want a buffer against the U.S. At least until the U.S. and China are comfortable as allies.
I suspect a main motivation for North Korea’s aggression is to keep the U.S. in South Korea, to maintain aid from China.
So as far as China is concerned, and not that many individuals can influence Chinese policy very easily, but improving U.S. – China relations could help diffuse China’s support for North Korea.
North Korea itself hurt its relations with China by testing its nuclear weapons, which decreased the region’s stability.
This post is obviously short, but I don’t see China changing its course because of North Korea. I mentioned it because I see potential there and that the main opportunity for progress there is to decrease tensions between the U.S. and China.
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EDIT: I included much of this post and this series on strategy (edited and polished) in my ebook, Understanding North Korea: Demystifying the World’s Most Misunderstood Country. I wrote the book to help increase understanding, communication, and freedom.