i don't like the level bonuses as a concept at all. basically, because population has no meaningful effect on production of money or resources (and is completely out of the players hands until you get pubs and so forth) they had to come up with a way to make people care about levelling. at the same time, because there are very few ways to control your population growth, they couldn't do what city levels should actually be for (limitting buildings: if the meaty production was limited to later level cities and they player had to choose between many cities and large ones, we wouldn't have the current mess). so they couldn't do that.

so they did the usual stardock and smeared a big, arbitrary, obtuse percentage bonus over everything, that isn't recorded anywhere, explained properly or have any reasonable explanation. (see gal civ 2, and the funky radiation that makes everyone have twice as much sex)

is gildar focus magical? then make it a spell. it is what i order my people to do? then make it something i can change at any time on the city management screen. is it an improvement? then make it a building.