Let's examine the situation here in AOC playing the 200 pop cap. 100 of those will be villagers maybe more usually not less if you want to continually pump out expensive units for awhile and get all the upgrades you needed for your army.
So that leaves you with 100 units to fight with(as stated above that might be less).
Now in AOM as some forumers have nicely pointed out you can support you economy with 40-50 vils. Let's take the high end here and say we need 50.
That leaves you with 65 pop slots open until you get to Heroic(actually more because most likely you will not have that many vils that early)
That gives you an army of say 25 foot soldiers and a few MU. Or say 18 cav and a few MU. That seems more than enough to me for second age battles(and remember you will have more because you won't have 50 vils that early).
On to Heroic you pick up say 3 settlements moving your pop cap to 160. That leaves you with 110 pop slots open( again probably more since you won't have reached villie limit to end of Heroic beginning of Mythic.)
Fight some in Mythic and pick up some more settlements, you can max pop out at 300. So that gives you 250 pop slots. That is 125 inf/archers. Or 83 cav. These armies are almost equal in size to the armies you have in AOC, so what is 10 or 15 units less really?
Come on you are whining about a minor issue(15 less army guys?) And since your oponent is going to be in the same situation the battles will still be a epic.
I think a standard pop limit is a great idea and helps to keep the game balanced, the important units are still important.
Another benefit of a slightly lower pop cap is that you will not run out of resources as often and be forced to use generic units the rest of the game(yes I know in AOM every unit cost gold).
I mean come on skirm and halb battles in AOC were just gay.
Okay I think I have said enough.