Units and Democracy

In Civ 2, Units stationed outside of cities in fortresses under a Republic do not cause unhappiness by citizens. I feel this is a very realistic concept and should be adapted to be used in republic and democracy government types in Civ 3. In Civ 2 however, Democracies do not have this luxury and units stationed in forts still cause dissent and eventually overthrow of government. In the US, military units are stationed all over the country in fortresses and people do not usually get upset at this, it's only when they go off to war (represented in the game by not being in a fortress). A good constraint would be requiring that the fortress be within a certain distance of a city occupied by that civ or an ally. And the dissent caused by one unit in Civ 2 is ridiculous, in a level 8 city under democracy, each unit away from the city would cause 1/4 of the people (2 heads) to revolt. Is that realistic?