A few things I would like to see in CS2:
When rezoning an area just to increase density, don't destroy all the old buildings all at once. Instead, demolish them only when new buildings can spawn on those spots. That mirrors more what happens in real life. The existing homeowners should also get a happiness malus because their lovely suburban neighborhood is going to get urbanized.
Different densities for industry and office. I like creating low-rise office centers in suburban areas because you see that all the time in the US. I can use the high-rise ban, but it would be nice if the low density office zone had building styles that look like they fit there.
Implement some of the features of the Traffic Manager mod in the base game. Specifically, I would like to see at least yield signs (or "give way" signs for those across the pond), lane connectors and/or turn arrows, and speed limit adjustment. Not having yield/give way signs in the base game was a real glaring oversight.
Give us a damn brush when putting down trees! I mean, seriously, it's in the map editor, why not the regular game?
And for the love of God, just unlock all the initial roads at the start. Don't force me to plop down one little piece of token roadway just to unlock them. Some of us are experienced players and like to use the one-way roads from the start to extend the initial highway.