Last Zone (SPOILER)

[Chyro]

If you activate NG+(any), it returns the zone back to the way it was. You can then deactivate it whenever to return it back to normal

Just quoting it for visibility. Don't know if people just overlooked the post. This is a very easy way to turn it back to its original state. Some people discussed that the NG+ of Dawntrail isn't out yet, but it doesn't have to be Dawntrail NG+, just activating any old NG+ state returns the map to its original state. Only thing is you can't activate NG+ while on the map, cause its so heavily affected by quest state. So head to a starting town -> activate any NG+ -> go back. And the map is its initial state.

Edit: Oddly enough, you can turn off NG+ while on the map and it instantly converts from original to current state. Wonder why activating NG+ on the map isn't possible then.