I'd like to see them tackle a SimCity that lets you choose from any number of time periods/locations/fantasy settings. Every SimCity has always seemed to be nestled firmly into the "modern cityscape" scenario (with minor deviations into "historic/futuristic" buildings and whatnot), but I'm curious to try and manage a medieval castle/town with functional feudal system and whatnot. You'd have to figure out how to manage resources and the economy using the technology they had in place at that time.
And if you went the fantasy route, you could even manage a town straight out of Middle Earth. Or rebuild Hyrule and Kakariko Village.