Variable Level Terrain Function

If possible could the Terraforming skill Level Terrain be made to have an adjustable interface option something like moving buildings? The idea is to be able to completely level off the tops of areas being worked on, not just the area right under our feet.

I was thinking something along the lines of when you click the Level Terrain skill it creates an area of effect circle which you could right click on to toggle the size and shape of it. Once selected it would level the entire area contained within its perimeter.

Maybe with advanced terraforming as our civilazation progress