Would it be possible to completely cut out the commercial bit?
Let's say you've already started a little Gambling/Tourism city, which is mostly packed with some residential (low+mid+high) and commerical (low+mid).
How would it work out if you build an, let's just label it "Industry/supply city" for fun, with mostly just residential, industrial, facilities (sewage, water, trash/recycling) and whatever specialization you might pick, let's say oil?
I'm just imagining a series of unhappy businesses which has nowhere to ship their freight. Will the residents of an industrial-based city commute (i.e become toursists/students) in other cities in your own region?
I maxed out the education level and industrial tech-level in one city I've been experimenting in, just to make sure my power plant wouldn't have a melt-down, worked fine, *phew*