I disagree with this in particular. Only having city centers on the map leaves urban areas spread too far apart, while some districts (especially infrastructure) make more sense elsewhere. I indicated this in another thread, but I think the problem with cities being so disjointed is simply nomenclature. They aren't really cities, they're provinces (settlements, colonies, districts, states, regions, prefectures, parishes, counties, pick the word you prefer). The city center is the local capital, while other in game districts are other cities in the province. Campus is a college town, harbor a port city, neighborhoods are like suburbs and small towns, etc.