Just wait till there is a terrain modification tool in Outerra.
Would be great be able to modify layers. Terrain itself generate holes, more altitude, less. Rocks layer for quit, add, redefine. And colors. So like if you change it in photoshop with brushes in diferent size. Changing intensity, saturation, change colors itself, and then the engine even fit the propper textures to those colours.
It will be that posible some day? This, plus some assets = Almost total Freedom for make any place in the world.