"Paint" a room

It would be fantastic when making caves and tunnels to have a paint tool that would determine the room layout. Basically instead of selecting a grid and modifying the corners to get the edges you want, just “paint” a selection, then when you confirm your selection it would create a selection of tiles with edges adjusted that closest matched your selection. So for creating a long winding tunnel it would be far easier as you wouldn’t need to manually adjust every corner to be the correct curve.