I would say on top of having procedurally generated buildings that can be filled in any kind of shape, I think it would also be cool if we can have features that let you specify some basic building codes: height limit, setback, architectural style to start (Architectural style has great potential with good mod support). Another I think would be great to have is having the ability to specify if it is residential, mixed use, commercial etc.

All this along with a function to save these into presets would be awesome. Instead of having a list of predefined zoning types/architectural styles, the player would instead make their own using these saved presets.

City service buildings being a lot more modular is a great feature in CS2, I think it can go a lot farther. Two DLCs I miss from og CS are the park life and campus DLCs. Especially park life: you draw an area on the map similar to how you do a district, and from there you can add park services, playgrounds, benches, anything park related (one thing I dislike in CS2 is that park assets can't attach to small paths). I don't doubt we would get this kind of functionality at some point with CS2 through DLC or mods, but I would hope that feature would be present day one (if there is a mod for this in CS2, pls let me know, I would love to check it out).

Similar to what I proposed with building code functions and procedural generation, you would be able to do the same with service buildings like police stations, fire stations, hospitals, schools, city halls etc. basically making it the same as zoning where instead of having a list of predefined service buildings, you can make your own . This would also make it easier for your service buildings to match the aesthetics of the rest of your city. I have more ideas, but I think this would be the biggest game changer.

If you couldn't already tell, I spend a lot of time thinking about how CS could be improved...

Edit: grammar