Dear Developers
At first, thanks for the game 
(sorry for my english, I am not a native english speaker)
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Stonewalls
I would love to build the walls naturaly like the roads with wide and narrow bendings and that the towers could be included into the walls. Also in My oppinion the wall design is a bit small. Would be nice of the walls would be bigger or add a third tear wall like a real city wall where also the soldiers can go up and shot like you have it on your title screen in the game or (like in Stronghold or AoE4). -
Quarry
A Quarry would be nice if you have Mountains or rock areas I think that would be realistic and a good source for Stones. -
Pharmacy
I think it could be a cool a Idea that a Pharmacy also could plant herbs and routs for creating medicin would be an upgrade to the normal collectors in my oppinion. -
AI
The workers AI could need some love. They just drop stuff everywhere when they are hungry or something else. -
Arrows
It would be more realistic if you would need feathers to create Arrows, maybe a collector could collect them in Bird nests where also eggs can be collected or … -
Chicken farm
A chicken farm could be included with corn/cerials as food and that would be a source for eggs and feathers.
Maybe you could consider some of those Ideas.