Oh on this I agree. This is what Ion was saying after all, they could do a visual upgrade. Just do what they did to Arathi but to the entire world. We've discussed this with @
Marlamin several times, it is entirely possible that much of this could be automated by simply replacing doodads and world objects (e.g. trees and buildings) with visually updated equivalents that are spatially identical. THAT can be done. if you respect the geography of the land, that means that coordinates for existing quests and for mob pathing etc stay the same.
Heck, this enters dream territory but they could fix the zone borders. Most of the zone borders are pristine, they do not have any quests or any mobs interacting with them. You can alter the terrain there without any issue. And then maybe, maybe revamp capitals only.
Then if there is a story they want to say in the old world for a heritage quest or something like the Blue Flight quest, just add a phase.