Suggestions for RTW:
- Consider civil population issues. Armies come from civilians (at least after Marius reforms).
- Consider number of civilians. Facilities must have a number of workers.
- Civilians have to eat. So you can siege and starve a city. Or you can invade a territory and harvest enemy farms (it was a extended war tactic). Or devastate them.
- Population growth depends directly of the amount of food, other factors could influence, but it is a natural law. So, the farms and upgrades would have a direct influence on the army's creation and the provincial workforce. The food is to eat, is not koku or florins. You can sell, anyway, the excedent. Keep in mind that in Rome, corn was almost free (demagogic policies) to keep the support of the poor people.
- Slavery must be a key factor in RTW. Sold enemies into slavery should increase the treasury and would have a dramatic impact in the labour force. So, the unnecessary workers could be soldiers with no influence on the city's development.
- More to come...