A nice thought, but diplomacy hasn’t worked yet, and it’s been about 65 years.

Military strikes are definitely out, since China would react very badly.  Even if that threat could be contained the end result would be another Iraq.

The only way North Korea will advance is if it comes from inside.  I have heard some heartening tales of purportedly illegal market vendors showing less fear.  If small acts of resistance like that continue, Kim’s totalitarian nightmare might come to an end.  Even his most trusted inner circle must be able to see that the man is unhinged, and if they sense that the populace has finally had enough of lies and privation,  they might well stage a coup.

Would that coup fix things?  Maybe, maybe not.  I don’t see a true democracy in the near future.  But a country that is less warlike and less barbaric in its treatment of citizens is possible, and would be a vast improvement.