Decouple Building Layers and Terrain Layers

I like being able to build multi story buildings but also like being able to have full view of the terrain.  With the current layer view system if I want to see story 1 or 2 or etc of my town, it stops chopping mountains and such.  So need to constantly toggle between layer and non layer to get both my town and terrain into perspective.

The layer view however works fantastically currently when trying to dig a mine as it makes it super easy to see where your going.