And how are you going to do that? Reorganising government not work well in Iraq. Do South Koreans agree to this? It might well be better to keep the countries split, you know.(i do not know)
From what i heard, the country is seriously indoctrinated, i doubt it will go down without a fight. Maybe Chinas way of trying to improve things might work, i do not really know how. Is that really Chinas rationale for dealing with North Korea?

Option (1) is definitely not going to work when China is still doing (2), and is option (3) really bad? Surrounding countries have their own difficulties, and simply do not know what to do.
I think option (2) is probably best. Just trade with the country, not considering it a sovereign government. In trade agreements, have demands that meddle with the internal affairs.