I suggest adding a way to add optional improvements to various buildings that player can add at their discretion at extra resource cost and some construction effort. Some examples could be:
- Beds at various work camps for workers to sleep at
- Extended storages at various buildings
- Stuff like lumberjack spots and sawhorses at woodcutters, small furnaces at mining camps, drying ranks ah high-tier hunters, etc.
- Storage sheds for fields - exclusively for seeds, fertilizers and tools
- Possibly some productivity improvements that would allow faster production at stations
- House improvements to improve morale and maybe give some buffs health/stamina buffs after sleep to residents
- Upgrades to fuel efficiency
Etc.
There's also a way to allow player making more specialized budlings instead of just straight maxing them out - limit the number of improvements a building can have. This way a player would have to choose between extra storage space, a bed to sleep or, lets say, productivity upgrade.
Having this feature the players would have a way to further customize their settlements and improve beyond just placing the buildings.