I like the Eleven Pillars idea, hinted at the linked post, and I would like to adapt it to out Earth. In order to do that, I'd need something like a heightmap, with adjustable sea level, to simulate the fog itself. It would be even better if it allowed me to raise or lower the sea level in different zones, but that's not a requirement.
If there isn't one with all these features, then even a simple heightmap would suffice, I might code the sea-level adjusting myself, somehow.
Since the aim and the inspirations are both RPG I posted here, but if you think there was a more appropriate SE for this specific task, this could be moved.