Roller for Terrain leveling

A Roller Vehicle to Flatten out Surfaces. Currently automatically done. but would be more realistic.

This would be really cool if mining and dumping left a surface that's level "on average" and needs to be rolled out to build on. It would be easy enough to do as something purely superficial (give the surface a bumpy appearance after mining/dumping that rolling levels out, while the underlying terrain level stays the same), but a more complete change of the designation system that no longer targets flat surfaces would be more interesting... if unlikely ever to happen.