I don't know about this one.
There are many urbanism models in the world. Which one is the best? I can't tell.
Which one should minimetro base itself upon? I can't either.
I just hope these different modes of layout/bonuses come with the different cities (or "choosing your won rules" dialog per game). This way we can include your idea of city center, which is fun and I would want to play, and some other people's ideas, which are equally interesting
My view of city center would be having all the uniques in the center (think: I want to get this rare stuff like hobby, job, concerts but they're only in the main part of town).
But it would make the game so much simpler and no fun
Having to route people to different uniques in different parts of town (or of the local region if you think of it this way) is what I like there. Just make sure there's a connection