I'm getting heart palpitations thinking of something like that being in SC13.
One of my favorite games was Railroad Tycoon II, they had many chains like that, that if added to SC13, this game would, in my eyes, be worth $200 and I'd pay it........(you didn't read that Maxis....)
Glassbox+RRT2 or 3-style resource chains=possibly the most realistic economic simulation possible
Here's an example of how some of the RRT2 resource chains worked for those who never played it:
Iron + Coal -> Steel Mill= Steel
Steel -> Tool & Die Factory= Goods
Steel + Tires -> Auto Plant=Cars
Steel + Food ->Cannery=Food (only available until sometime in the 20th Century when the Canneries stop accepting steel in favor of aluminum
Some maps, and some custom maps could have the Goods sent to a Port where they'd be traded for something like Rubber to feed into another resource chain, then the Autos for something else for another resource chain.
Cities would consume Passengers, Mail, Autos, Food, and a couple other resources I believe.
A bit off topic but if you really like these kinds of games, you should try Capitalism II. So far the best economy simulator I've ever played (and I also played RRT series).
