Or a lot of slaves.
It's a common misconception that slaves were the preferred method of building complex structures. Sure, they were probably used for the most basic tasks.
The Forts to development ratio for tradition is also a little out of line.
You're not supposed to max it out, but you can If you really want to.
Great ideia! I like it!
I like this idea as well. A free fort per government rank could make it work much better. And the age bonus could also be changed to add another free fort per government rank instead of "free forts adjacent to rivals", which you have, like, never.
Forts would be way more useful if you could actually keep armies inside them like in reality.
Forts would be most useful if they could bloody shoot back instead of just waiting to be sieged down. However, the sad truth is that most 90 % of casualties in this period were to diseases and hunger, not to weapons. I'd still like to see navies get at least some damage when trying to disembark onto a fort.