The Pillars of the Earth
There are cities, population, commuters, and migrations. There are social econometrics as unemployment, wealth, crime, and education. Cities grow and evolve following the equations developed in the last decade in the field of sociophysics. It's the scientific state-of-the-art. Zipf's law, Gibrat's law, Gravity Model, etc. (see references below), those are some of the principles of the equations we use. If a player becomes mayor of a city, he can take the control and make it growth getting money from the taxes, if he does it properly. Just as in SimCity, with residential, commercial and industrial areas. However, now the player can use this money to found industries or build an army and increase his influence in other territories. The player can pay for electoral campaigns in other cities to expand his territory, or for bribing local authorities for taking the control (buying it to another player), or for using the army conquering other places by force. For protecting his territory, the player must ensure that he build enough social services to have the support of his people and an strong police or military force for preventing eventual attacks. The design and graphics for buildings are also procedurally generated according to the climate, culture and size of the city.
Memory-endowed US cities and their demographic interactions (A. Hernando, R. Hernando, A. Plastino, E. Zambrano, J. R. Soc. Interface 12, 20141185, 2015).
Space–time correlations in urban sprawl (A. Hernando, R. Hernando, A. Plastino, J. R. Soc. Interface 11, 20130930, 2014).
The workings of the maximum entropy principle in collective human behaviour (A. Hernando, R. Hernando, A. Plastino, A. R. Plastino, J. R. Soc. Interface 10, 20120758, 2013).
Scale-invariance underlying the logistic equation and its social applications (A. Hernando and A. Plastino, Phys. Lett. A 377, 176, 2013).
Thermodynamics of urban population flows (A. Hernando and A. Plastino, Phys. Rev. E 86, 066105, 2012).
Variational principle underlying scale invariant social systems (A. Hernando and A. Plastino, Eur. Phys. J. B 85, 293, 2012)
Unravelling the size distribution of social groups with information theory in complex networks (A. Hernando, D. Villuendas, C. Vesperinas, M. Abad and A. Plastino, Eur. Phys. J. B 76, 87, 2010)
There are natural resources and companies exploiting them, covering the full chain to the final consumer. For instance: if the player finds iron in the mountains, he can build a mine to extract the ore, which is transported to a refinery to produce processed iron, which is transported to a factory to produce goods, and get some benefits from it selling the good in the commercial areas of cities. Or he can use the iron in a military factory to produce tanks or arms, that's up to him (he could directly buy the tanks with the money but that's under his strategy). We have designed an economic tree with more that 40 kinds of buildings/industries and up to 100 kinds of products/cargo/resources (see the full tree here). The inspiration here is Transport Tycoon or The Settlers, but using the equations from econophysics for automatizing the economic flow and evolution. A single player doesn't need to fulfill all the economic tree to be successful. As in real life, you can be specialized, earn money, and use that money for trading and get the things you don't produce yourself.
Thermodynamics of firms’ growth (E. Zambrano, A. Hernando, A.F. Bariviera, R. Hernando, A. Plastino, J. R. Soc. Interface 12, 20150789, 2015)
For connecting cities and industries, you need roads, trains, ships, and airports. The reference here is Transport Tycoon again, and we will just copy the management system developed there (we can get inspired by the open source openTTD). Cargo needs to be transported from one industry to another, as well as commuters/passengers. The player can build roads, trains, ships, airplanes to fulfill these goals. It doesn't need to be your own cargo: you can connect other players' industries or cities and receive the benefits from that service. You can rent your train stations to other companies as well. You can build a port and buy any kind of cargo for reselling it to the local industries (even if it's not clear the legit origin of that cargo, but maybe that's not your problem). Cities are connected by a system of roads following the equations described by sociophysics, so the basic flux is ensured. Indeed, the player can improve it and find business opportunities anywhere.
Road Trees (SThAR - EPFL - CASA)
Anything can be sold, or exchange, or rented. From elements of the game as trains, companies, cities, cargo, or territory, to information, military services, or business alliances. As mentioned above, we will use blockchain technology for this purpose so the process is decentralized.
An army can be created to conquer the world. However, it is not mandatory as in Age of Empires or The Settlers, it's just another strategy to scale and earn money. Building and maintaining an army is expensive, so it is not necessary the best strategy: it consumes a lot of resources and has a very high risk. But it's fun. Or probably you will need it for defending your territory from others. Controlling a territory is done as in The Settlers: your buildings define the area under your control but your army should defend it as in Age of Empires.