Having each case be a numerical range rather than a specific setting for each specific civ would allow the civilization to also slowly change its ethical structure due to surrounding events as well. Dwarves allied to Elves would work to increase that elvish culture's tolerance for wood-cutting while at the same time increasing the sensitivity of that Dwarven civilization to wood being cut. I imagine the various civ's wars would be started over variables that are more than a threshold's value in these traits and average out the values over a span of battles until peace is made with a compromise because one or the other civ has changed enough to have their ethical differences be below a specific threshold of difference.
Obviously, those that win the battles would change the cultural values of those who lost them, so that one culture could eventually have a disproportionate effect on the world.
Other mechanisms than wars could change a civ's cultural values as well, such as children becoming more or less precious depending on how many exist in relation to the adults and the total available food at the time they're checked - likewise, the creation of artifacts might be increased or decreased depending on the ratio of civ members to available food at the time they're checked. (The idea is that surplus food gives people the time to indulge in "The Arts", while a scarcity of food decreases the chance that people will think about great works of art over trying not to starve/keep their families from starving.)
What's really interesting about this concept is that a Player's play-style in Fortress Mode could directly impact the reactions of the Fortresses parent civilization to it, either holding it up as the shining example of dwarven culture by making it the new capitol or breaking off all relations, sending no more migrants/caravans, or even sending an army to conquer it if the Player's actions cause the Fortress culture to pass the tolerance threshold far enough.
The fact that play-style would seem to be coupled with an exterior world would increase its sense of immersion considerably.