Snarkhunter, I don't think we disagree. The historical picture is indeed complicated.
Ed-Firaxis:
'Jaybe is correct about the thought process behind Feudalism. As people began to migrate towards the cities, Feudalism broke down and maintaining a strong army became much more difficult.'
By the way, when Ed-Firaxis says 'As people began to migrate towards the cities, Feudalism broke down and maintaining a strong army became much more difficult', I assume he means within the old Feudal system, not that cities didn't have their own means to raise a decent army.
Yeah. . . if
that's what he means, then I think I have to pretty firmly disagree with him, especially after reading Marc Bloch's work on feudalism. This is Eurocentric, mind you, but Europe as a whole was undergoing a pretty significant population expansion throughout the Middle Ages, and the growth of the towns did not, in general, depopulate the countryside (& make it harder to raise feudal levies). in fact, you can make a pretty good case for Europe reaching max pop in the 1200s, & not reaching that level again until nearly 1600. Since in game terms it's all one big generic unit support pile, the distinction between town/city seems ahistoric at best.
And that doesn't even address how feudalism worked in towns & cities; both tried to escape the control of the demesne early on--and the feudal lords fought the tendency tenaciously. Controlling a town was like a license to coin money, literally.
But like I said, the way Firaxis set it up you get a lot of towns and not many cities, and that's not a bad approximation in modern terms. It's just not really the right reason, is all. Not sure what would be better, because the game doesn't really have a concept of cultural loss: once you know how to build aquaducts, you can always build them. Otherwise, I would say in the MidA, you should lose aquas & rivers should give no growth limit escape; the requirements for expanding pop should double or triple; disease should strike randomly at all towns/cities & kill off citizens. You'd go into the MidA with some cities, but would lose them over time & wouldn't be able to re-create them until some later tech. Then change the feudal unit support. Now cities become precious jewels to be protected from loss at all costs, because you can't recover them for a while if you lose them. But it would add some grit to the game, & I'm sure there would be a lot of unforeseen side effects. And it might not reflect non-European feudalism too well.
I don't know the editor at all. Are there enough controls in it to simulate a Dark Ages type disaster: declining resources, massive invasions, infrastructure decay, etc? That would be an interesting challenge: how low do you have to sink before clawing back up again? You'd remove democracy & republic as governments, if possible.
kk