Non-rectangular mining tower area designation

I want to mine while also at the same time fill the mined area with waste products. Sometimes the areas overlap and then wrong product is getting dumped in location it's not supposed to or excavators mine in wrong places because there's another mining operation nearby.
Make the mine control tower area assignment to be similar to mining designation tool, except it has to be one continuous area (not necessary, but then it would be harder to find tower's designated areas, unless there's the view area button). You can pretty much keep the rectangular selection, but give it add/subtract modes.