I can see why you would want to add NPC’s, however, like others have said, it did seem a bit out of place in this particular game.
The idea of quest boards that players can create their own quests is a good one, I think.
Craftable quest board, but only one per settlement, only the warden can craft and place. And everyone that is part of the settlement can post quest.
Let’s say it starts simple with fetch quests for rewards.
Everyone can craft a quest completion stand to place in their own beacon, this is where the quest is designed. Once the reward is added to the stand a token is generated, then the token is placed in the communal noticeboard.
Reward can be coin or items.
Eg:
Citizen creates ‘collect x inky leaves for fancy gem hammer’, place fancy gem hammer in completion stand. Token is generated.
Take token to communal quest board, stick it in, quest appears for public to view.
Adventurous citizen checks out board, thinks I can get those, or already have those. Takes token, quest is activated.
Takes quest token to completion stand, inserts token and inky leaves, is able to remove fancy gem hammer.
Quests can be time limited, after 24 hours token returns to board for example.
Citizens can be limited to how many created quests they can have at any one time, and how many active quest tokens they can collect at any one time.