Cities gain a growth bonus of up to +3 based on the ratio between current population and maximum population. Pioneers reduce population by 30 when put in the construction queue which allows the player the keep growth at +3 regardless of grain yield/food output by micro-managing pioneers into the queue whenever the growth bonus drops below +3 and pull them all out when there's enough population for a new settlement level.

The advantage of using the pioneer bank is significant especially for Empire factions (due to the lack of alternative sources for city growth bonuses) and in the early game and it seriously devalues grain yield compared to materials and essence when picking spots for new settlements. A city with a grain yield of 2 will grow just as fast as one with 6 and you can even use the bank to store any population in excess of the city's population limit until sufficient food buildings can be constructed.

I'd like to suggest that city growth be tied directly to grain yield instead by providing a +0.5 growth per grain yield. In addition to being simple, this model has a number of advantages over the current one:

- No growth advantage of using the pioneer bank (less micro-managing)

- More interesting choice when picking city spots. Do I want a fast growing city over one with higher production or more enchantment slots? Especially interesting considering that growth cant be rushed (at least until consulates become available for outposts).

- Gentle rain vs Nature's bounty becomes a choice between having a larger city vs. a faster growing one and may actually lead to some enchantment changes as the city matures.