There can’t be a sudden reunification, imo. Although, China would push for that, just to mess around with Korean politics.
I would probably install an interim government to take control of the country and install small changes along the way until they become compatible before any unification can be formalized.
This is a three generation project, imo.
That’s my problem with who they went to for advice. That reunification seemed peaceful, but it was sudden and there are tons of malevolent undercurrents still.