Maybe it'll be like in chess: one unit per turn.

How's that for a simple system?
While it's been reiterated that Civilization is not a war game, what kind of game
is Civ, exactly? It's not simply resource trade, as the game makes for some fairly complex economic wrangling (like Railroad Tycoon), but it's not simply that; it involves territory acquisition and resource extraction -in no small part to fuel those trade machinations- like Catan, for example, but it's not just that, either; there's territory improvement and city building (think SimCity), diplomacy, exploration, and cultural development. All of these are modeled in fairly complex abstracts and mesh into what Civ is, which ultimately is the development of human cultures and civilizations.
And at the end of the day, a good deal of human development and civilization has involved warfare. Wars over resources, territory, and population and trade centers are just as important in the game as they are in real life, and the game must take that into account. The SOD is ugly, but in some degrees, just slapping it with the catchphrase "Civ is not a war game" is disingenuous, as it skirts around what exactly the game is, which would be more aptly described as "so much more than a war game." It may be far simpler to just run with one unit per tile, but in a game that builds such a complex model of all aspects of human development, why should war be marginalized to an abstract?