Separate forest meshes for hills and flatlands?

[OnmyojiOmn]

I've been thinking about making replacement forest meshes, but it seems like the same meshes are used for both hill and flatland tiles. Is it possible to create separate meshes, so forests on hills actually sit on top of the hill?

Barring that, is it feasible to create some kind of special "forested hill" tile, maybe as a feature?