The massive loss of life an artillery attack across the DMZ has been the North’s hole card pretty much since the suspension of hostilities. Fat Boy wants an equivalent threat to Japan and America—America particularly. He won’t stop until he has a believable nuclear threat. He’s perceived that not having the nukes aimed at the Continental US will detract from his prestige and power at home. There is no solution other than yours. However it’s really, really dangerous.
Japan SK and the US hot the artillery along the border, the test and launch sites and someone try to stop a drone rocket in his lap. All at the same time.