The answer is not much beyond what we are already doing. It's not a question with any easy answers.
I have decied now as age 70 approaches in a few weeks that almost anything is possible if we work at it hard enough, long enough. History and world events were unimaginable which have come to be, both negative but more importantly positively in my lifetime.

Hydroponics for farming in N. Korea could help make up for the lack of land there, there is plenty of plain old water last time I looked.

Being a simplistic person myself, the old "beans and bullets" economics courses many of us studied in undergraduate college still is the order of the day for most every nation on the face of our tired globe...which of course includes North Korea.

Aside, if backward Libya can move as it has away from nukes and terrorism into the mainstream of the world's free enterprise system, then this is proof broadly speaking that "anything" is possible.

It will take a pragmatic mix of all points of view from all the free world's nation's political parties and leadership, but something better sooner vs. later for North Korea can be done.

NOTE: I have a "prejudice" to admit here for wanting to see a better way for both Koreas. My late older brother was drafted into the Army and served in the Korean War during the early 1950s. A Second Cousin, a West Pointer who chose the Air Force to become a pilot when we had no Air Force Academy, was shot down and killed by a Russian pilot flying a N. Korean MIG in 1950 over North Korea. My late first cousin was wounded as an Army Company Commander in North Korea in the Korean War.

We can put no more restrains on N. Korea than we have been able to do on Mainland China...and remember that Mainland China is "the bank" for US foreign debt today, no small matter. There is no more room for "if we control this, then we can safely agree to do that" thinking, in my humble view, using the China model.

Of course N. Korea will never be a China, but given a strong wind at their backs, N. Korea could be someday at least an economic model or "cousin" of S. Korea.