How about making it in such a way that the additional buildings available depend on the outpost type?
Storage space could be added to all types
Watch towers only for stronghold or border posts
Barracks only in strongholds
Workshops only for workshops (sounds kinda silly though)
Farms might be able to boost something in regards of raw materials or make it possible to have a herd of animals for some purpose.
Trade posts... maybe food supply for mektoubs or a shop
Diplomatic outposts could host food supply for mektoubs as well
Research centers some kind of trainers teaching special skills
Magic poles could make a building increasing the sap generation of homins in a area around it
Storage space could be added to all types
Watch towers only for stronghold or border posts
Barracks only in strongholds
Workshops only for workshops (sounds kinda silly though)
Farms might be able to boost something in regards of raw materials or make it possible to have a herd of animals for some purpose.
Trade posts... maybe food supply for mektoubs or a shop
Diplomatic outposts could host food supply for mektoubs as well
Research centers some kind of trainers teaching special skills
Magic poles could make a building increasing the sap generation of homins in a area around it
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