Well there is a script able way around this and a mesh illusion that could work for this.
In a model program you could make a round mesh with a texture on it, Maybe some hills as you want. I would not go to crazy at first, because this will take a bit to get used to.
Objective:
Import an object as a terrain facade, Sculpt the GameGur terrain to that, (for AI collision) Then turn off the terrain thru Lua script and you will have the appearance of AI walking on your terrain. Script in the scriptbank folder already, place it in a trigger zone and have the player walk thru it.
You can make the smaller then the real world. maybe 2000 unit diameter or 3000 unit diameter.
Then you are further from the skybox edge, the terrain and water planes are invisible but collision is there, and then the Fog should work better for you as you are away from the max distance.
Some clever plane blockers with a great texture should provide the rest of the illusion.
Hope that helps.
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