I'm still a bit at a loss to understand why we would need to manipulate upkeep with a building at all... why not through civics alone? It should be acceptable with the first default civic choice to have the player REALLY want to get off of that civic asap when growth begins to take place.
Because if we set the first city to not give any maintenance, or up to -1 or -2
at most at higher difficulties, through civics alone then that will persist through until going away from that civic, and that would increase the problem with big drop in income some experience when switching.
Using a building can offer alternatives like reducing the effect over time so the drop between new civics is reduced.
Of course one could also argue that players should plan ahead and be prepared with the right buildings, not have expanded too much, and so on, before switching, but we also need to consider the AI. A sudden change they are or are not expecting can help stagnate the AI.
If they expect it they might not switch until much later and lose a lot because of that.
If they do not expect it costs could increase to the point where they will find themselves in a bind.
With "expect" I not only mean the initial cost, but also projected cost from a) more negative cost buildings, b) more cities, and c), the big one, higher population in the cities (this one is doubly as it also increases -Education and could drop commerce and science a fair amount too).
Now if you can set a change in the Civic on City Maintenance by techs learned then that would work just as well, but I am thinking that is not possible, though a building (or several, each with -10% and obsolete by vital techs, and then not limited so they do not take National Wonder slots) is?
Cheers