The idea is that you could purchase a “specialization†for a city, giving it a significant boost in one area. Currently, whatever is best for one city is best for all cities; you can specialize your cities, but there is no reason to, and it can become mildly disadvantageous to do so. This would add another layer of strategic depth to the city-design aspect of the game, and create more “deep†build options, in addition to "tall" (more infra) and "wide" (more cities).
Some thoughts on what city specializations could generally be:
-Raw resource boost
-Manufacturing boost
-Commerce boost
-Military boost
Although, what I’d really want to see is something more specific and dramatic, rough examples being:
You could purchase only one per city, they would be somewhat expensive (though not as much as a national project), serve as a resource sink, and they would work off of and trigger the same cooldown as projects and cities, making that cooldown a bit more meaningful. Specializations could be replaced if you wanted to gradually shift focus.