Is a fog of war type thing on the map like Morrowind possible to mod in?

It's there on the local map. At least I think it is, I have not been in the local map above ground for a long time.

The world map works the same way, just the fog reveals map markers as it goes away. Or, do you want a fog on the World map also?

Fog on the world map also. I like how Morrowind's world map became more detailed as you explored.