Agree with most points above, but two
> More punitive end-game environmental effects, more environmental effects in general (Earthquakes)
Depending on implementation and AI handling. Rising sea level as it is now almost kills the game for me as the only way to counter is are highly-intrusive (in terms of "presence" and "visibility" in the map) improvement. Would not mind increased disaster levels and specific buildings/infraestructure to counter them.
Maybe, disasters would be more interesting if you were able to flexibilise city positions and there were not, as traditionally, fixed from first location. This brings me to the second point
Honestly? I would be okay with specialty Districts being gone. I like the idea of utility districts (Airports, Harbours, Suburbs, Aqueducts/Cisterns, Resource Silos, Fortresses) and the current placement rules for Wonders, but specialist buildings belong inside the city centre i m o. Replace them with more buildable infrastructure.
I am not sure "specialist buildings" belong to the city center. Instead, I would say some city centers have grown up out of "speciality Districts", and that is why we consider now speciality buildings belong to city center. I.E: many, old and new university campuses were built in a quiet location outside the city center, but as the university become involved in other topics, a
new city grew around it. Maybe the exception could be TS and EC (whose buildings might belong in city center or neighbourhoods/suburbs, but I think Campus, HS, CH, and IZ follow more this philosopy.
In that sense, It might be interesting to push an idea to see different types of city.
> Administrative: the ones you settle, with Palaces and gubernamental buildings. Provide improved loyalty. Also, you could include probably here those that could be achieved by promoting an Encampment to "city" status. They would starts with walls
> Universitary: achieved promoting a Campus to "city" status. Bonuses to science production (probably to culture as well)
> Economic Hub: achieved promoting a Commercial Hub or Industrial Zone to "city" status. Bonuses to gold production. (Note I think it makes more sense to nclude the IZ than making a "production" city as a super-manufacturing city normally is subject to an Economic one that controls the output of that production).
> Pilgrimage site: achieved promoting a holy site to "city" status. Bonues to faith production.
Any city, on the other hand, any city could be "demoted" to a "Historic City", with district-rank, and associated to a different city, and providing a tourism bonus. This would allow to mimick real wold rise&fall of some cities which were once great but lost preeminence to other cities due to wars and conquest, shift on peoples needs, or natural disasters/change on environment conditions. Cities bult out of a speciality district will contain (or be able to complete) the buildings of its origin district in the city center, maybe with increased specialist bonus, along with the city center districts themselves.