Ok, let's consider this:

If total population among all cities is used:

4/5 cities all barracks
4/5 cities all cottages

Base unit production based on total population = 182,250 (give or take)
The proudtion speed is now increased 4 to 5 times. Half the base but 500% faster = 250% overall production. 461,250 base units at a good prouction speed.

If total population within each city is used:

(multiply by 9)
15 barracks + 16 cottages
72,000 base until production per city at a really good production speed.

No matter how we break down the population angle, there is plenty of room for abuse and exploitation.

"An army marches on its stomach." ~ Napoleon Bonaparte

(I wonder if anyone will catch what I did. )