If you wish to replicate what happens prior to building a city plan, you can already do this. The gavel tool has an option to demolish the settlement and I'm pretty sure there are options to do likewise in the city manager holotape. It's been so long since I've used them that I can't remember the exact locations and wording.
If you wanted to put it back to how it looked before the player or Sim Settlements ever touched it, that might be a useful tool. In theory someone could just go around the settlements and make template plans of the untouched settlements which players could then use to 'build' it back to vanilla. The tools to do this are already in place should someone have the time and the patience.