Limit to number of non-upgraded residential buildings you can have in your city?

You can only have 5 zones available for upgrade at any one time. That does not include zones upgrading for the first time. So you can have 5 mid level buildings and 3 undeveloped zones with builders hat icons on them. 8 in total. If you upgrade one building, in the time it is being built, the hat icon will switch to another building ready for upgrade. You have no choice over this. Hope it makes sense. This is one of my massive problems with the game, I, like you, want variety to build a realistic city and want to keep some of the buildings you see in the upgrade process, houses, condos, tower blocks, trailer parks, medium scrapers etc. I don't want all glass skyscrapers that look the same just to chase population. You basically have no control over what buildings to upgrade, which is not good. I downloaded the game after looking at the advertising, which shows building variety and if you visit Daniels City you see it there as well. You have no way to achieve this and it annoys me. I want the developers to allow us to toggle the builders hat icon and allow us to choose which buildings to keep or upgrade. Then I will spend money on parks or more content such as landmarks or specific buildings. Such a disappointment, this game could be amazing, the graphics are great but I'm so bored of only having a choice of 6-7 glass skyscrapers I'm on the verge of deleting the app. Cheers.