"old town" District cosmetics from previous ages

I love the great effort that has been put into making the districts and cities feel alive and atmospheric. This works extremely well in the early ages but the cities can start to feel somewhat impersonal in the late game.

I would love to see a feature in the game where the districts visual does not automatically update every time a player progresses to the next age, instead the existing districts keep their old visual appearance, whereas new districts will have the visual of the current age.

This way there would be a distinction between the old town with districts from previous ages and a new town with districts from the current age. In my opinion this could give the cities a lot more character and would allow players to "read" the progress of their cities throught the ages. Much how it can be done in the real world with historical cities such as Rome, Jerusalem or Cuzco. Take the latter, If you stroll through parts of the city you can see Remnants of the impressive Inca temples next to spanish colonial districts next to contemporary housing.  

Of course if someone should decide that for aesthetical reasons they would prefer the visual of the current era this could be handled much the same way as administrative centres are handled already where the aesthetic of the administrative centre can be updated (for free) in the construction queue.

As someone that loves just pausing the game from time to time, watching the variety of sceneries that my cities offer, I think this could be a comparatively simple mechanic to implement that could potentially greatly enrich the visual appeal of the cities in the later stages of the game. :)