Vector-based roads, along with geomatics.
Zoning that includes pipes. I hate laying down mains - you only need that to connect two areas together to the network. Make it like power. The only things you chould be concerning yourself with is water pumps and water treatment plants.
Updated mass/public-transit solutions and power solutions. Include aerial tram-lines that hang by wire (ala Portland) or that follow bridges (ala NYC), high speed rail between regions. Even include Rapid Personal Transit, unfeasible as it may be. Layered roads would be nice - adds a massive amount of capacity along the most highly congested roads. Fusion plants using giant vats with tiny cyclotrons outputing GW of power.
As for Societies, include immigrant groups moving in, possibly taking over neighbourhoods or building new neighbourhoods, affecting architecture and the sort. That would add a massive touch of realism to the game. It would pretty much give the ability to set up your city to have the ability to be placed in varying countries around the world.