One thing that I find always lacking in most strategy games with civilization building is that the biggest cities always seem to be the ones that produce the most food. In the Civilization games this has always been the case as it has been in Master of Magic, Galactic Civs, and most others (Master of Orion 2 being an interesting exception.)
In Elemental, however, it's unclear what the relationship between population growth, food, and prestige will be. Yes, we know that food supports people and prestige attracts them, but the big question in my mind is whether food is a consistently moveable commodity.
If I had my way, I would make food more easily transportable as one researched "caravan" and "road" techs to simulate the growth of a more complex inter-empire trade system. Initially, population centers would revolve around food sources, but eventually, once food can be transported easily, population would gravitate to wherever the prestige was, and prestige arises from wherever there is industry or special features. For instance, you might build a city where there is poor farmland, but it might instead sport a thriving lumber mill, a river, a holy site, and be at a critical trading crossroad. If there is enough food elsewhere in the empire to be traded with Acacia to support a larger population, it might grow massive and thrive because of the convergence of elements that add prestige to the city. The city might also import food from foreign sources as well.
Is this version of city building going to be present in Elemental? The prospect mentioned above would definately add extra strategic considerations to the game (small farming cities that support large population centers would be appearling targets in warfare) in addition to adding some interesting city types that you infrequently see in strategy games. For instance, I've always wanted things like bustling "Oasis" cities arise along vital trade routes like those along the silk road or like those in the Sahara Desert between the Mali Empire and Europe. A system like the one above would make this possible.
