[Suggestion] City Building Upgrade optional
When a city reaches the required level or you get the required tech it automatically upgrades the buildings. It would be nice if there are an option to not upgrade, especially for modding in the future. But I also noticed a potential balance issue as when I unlocked university tech it now replaces the schools automatically and the university buildings cost 10x as much.
While I have no real issue with that fact that the buidling cost more and produces more the fact that you get the upgrade for free does seem unbalancing. Before this it seem the buildings such as housing cost the same regardless of level. Which I've also always thought was a little off since villas house over double the amount as huts yet cost the same. But given the free upgrade system it would be a bit unbalanced to have them cost different just like it is with the university. Yet at the same time it seems rather limiting to not have the option to choose upgrade and pay the difference.
I can think of 3 ways to potentially handle this.
1) The way the school and university were setup before but that is really not "upgrade" as you simply have to demolish one and replace it with the other.
2) A city wide upgrade option where you pay the difference to upgrade the buildings. This could potentially be automatic and simply withdraws the funds when your meet the requirements and have resources. Though players might find this annoying as a city leveling would suddenly automatically start spending a lot to upgrade. So a manual option would probably be preferable.
3) A mix of the current build system with the way resource terrain tiles work. What I mean by that is take housing for example say you have a hut and can now build housing in the city. When you select housing both the empty tiles and the hut tiles are highlighted. If you choose to build on a tile with a hut it cost the difference in time and resources. If the buildings take the same time to build then some arbitrary minimum of maybe 1 turn or some % of the original build time.
Though another potential issue does arise from this. It's likely the auto upgrade is a way to get around the buildings of the same grouping sharing the same limit. Since your only allowed to build as many buildings of a curtain type as the level of the city before you could have 5 schools and 5 universities in a city. Since they are now on the same upgrade path with auto upgrade it means you can only have 5 of which ever is currently allowed in the city. So the addition of of an over arching building limit would be nice as well. Such that you can only have a total of 5 schools & universities in any combination. Again this would be very handy to have for modding and could allow for city specializing buildings kind like national wonders in Civ4.