As an example of the importance of public opinion, consider discrimination. Cultural discrimination caused the Persian wars of ancient Greece. Religious discrimination caused the Crusades. Racial discrimination caused the Nazi invasion of the Slavic lands, as well as the Holocaust. Economic, religious, and cultural discrimination motivated Stalin to initiate the Cold War. And racial discrimination helped cause the American Civil War.

Similarly, the downfalls of many leaders have been cause by failing to address corruption and crime (modern America, ancient Rome). Also, opinions on national defense have determined how much the people would support war or preparations for war (Vietnam versus WWII). So clearly these are fundamental aspects of history.

Basically, one needs to attribute more variables to society, in order to differentiate between classes of people, and to measure motivations for people to be more worried about crime than, say, education. Some of these variables would come from political/economic systems. Note that I'm treating politics on separate footing from economics. In Civ, the political system determined trade to a large extent. Thus, the ancient Greek republics got the same trade bonuses as a modern republic.

One needs to introduce notions of capitalism, communism, democratic socialism, feudalism (aside from its political aspects), and bartering. For instance, modern Sweden may be said to have a democratic govm't, and a democratic socialist economy.

Besides added systems and system factors, we need more flexible variables, sensitive to the state of society. Such variables may be average income, income polarization (top 20% vs bottom 20%), education levels, health levels, unemployment, and religious persuasion.

For example, to determine average income of the top 20% of society, we may assume it fluctuates over time as a sine curve, reflecting the cyclic nature of business in any era. The amplitude and average of the wave may be determined by the system, while the period may be hardwired (say, on the order of a decade), or system dependent. The total average income may be gotten by averaging the averages of each quintile of society.

As another example, some religion and tradition may be seen as sedatives, compelling people to simply accept their lot in life (eg - catholicism and feudalism). Then the level of sedation may be modeled as a decaying exponential, with its initial value and time scale determined by the political and economic systems. This means that, eventually, people will not be so blindly accepting of the injustices in their lives, and will demand change. It might even be a challenge for a player to satisfy their demands before a revolution occurs, and the player is executed! If the general happiness level is below 70, say, for 4 turns, then revolution occurs. This forces change on the player, making him adapt to the needs of the people, instead of the more common situation where the Civ player jumps immediately from despot to democratic president.

Much of public opinion is dependent on the priorities of the govm't. Govm't domestic priorities, in any age, are usually reflected in its budget. If the govm't gives massive funding to education, it's less likely to be a concern for society. So I think that the player should set funding levels for different purposes (education, health care, crime, welfare, religious tithes, etc) and that this should impact on public opinion.

So, for example, the difference in avg. incomes btwn the top 20% and bottom 20% would be determined by some system factors, plus welfare funding levels determined by the player.

It's just that ancient people were more easily pacified than modern people. Religion sedated the serfs and lower classes in Egypt, medeival Europe, China, and pre-Ghandi India. They saw their stations as eternal, with no notion of social mobility. But when their opinions became strong, and actions overpowered less tangible ideas, the people reacted.