Indeed!
The largest problem I will be tackling is simulating (to the best extent possible) an economy. One thing I liked (and made a lot of sense, at least to me) in SimCity 2000 is that the first demand you had to fulfill was industry. So the player will choose an industry to build their city around (though they'll be able to diversify any time. The price for that is possibly losing their edge in said industry).
One of the goals in the game is cashflow. Each service/industry/utility (SIU) that is outsourced is lost tax revenue for the city. For example, a new map will contain national power lines running through it. You'll have to tap into those for power initially. This means your citizens will pay a higher price for electricity, which limits tax revenue in two ways:
1.) You're not taxing the profits of the power plant
2.) You're citizens have less money to spend, thus the businesses in your city have smaller profits to tax.
Now iterate that math for every SIU required (which depends on city size).
To counter this, the player starts by owning all the land, so the city's initial revenue is from property sales. As the city grows, land value goes up. (Fun point, once the land is sold, its permanent until you can afford a great lawyer on your board to win an eminent domain case).
Over time the city will grow and more SIU's will be localized, increasing the cash flow of the city (more tax income). But, to attract/retain talent (thus have larger corporations), the city needs to spend this cash on services to make the city a desirable place to live. I think some fun side goals would be, for example, attracting the best chefs, artists, musicians, that are available, and have them e.g. open a restaurant in your city.
So, the macro scale is competing against other cities (both for talent and services/industries). I could say the winning condition is to be at the apex in every industry in the game, though that will likely be impossible, and I dont plan on having any real win condition.
I haven't sat down and mapped out how to simulate the competition (other cities), but I dont see a need to simulate each city at the micro level. I believe DF takes a similar approach. If anything, an infrequent mass calculation could determine who moves where and why, and to compare business competition. Im using SQL for storing game data to take advantage of what it does best, so this should be relatively easy.