And what about UN sanctions? Even transferring the Yak-130 or Kilo 877 would still be too bold.South Korea isn't just selling ammo to Ukraine. They are also selling lots of military hardware to arm Poland to the teeth. This includes tanks and artillery.
I am fairly sure that Russia will try to be restrained, at least initially, and it is likely that lower tier hardware like the MiG-35, Yak-130, and Kilo submarine will be sent. If South Korea then sends weapons into Ukraine, then this could be upgraded. Higher end weapons could be provided. Lada submarines, Su-75 when it is available, etc.
Licensed tank production could also be furnished to North Korea just like they setup T-90 tank production in India. Or aid could be furnished to help improve North Korea's own native tank program.
I consider the ideas of circumventing sanctions which was mentioned in The Diplomat, or transferring technology for local production like some of the ideas you just presented to be more feasible.