So I read somewhere that one of your longer term goals for Stonehearth includes the Hearthlings having relationships with one another. Making friends! I think it would be amazing if you could assign certain buildings to be owned by certain Hearthlings (most likely whoever’s bed is in the building, but may be best to give it more flexibility anyway) and only that Hearthling’s friend(s) can come inside at will.
To get even more specific, you could set specific rooms in a house to be restricted (personal/home) or communal (a workshop/market). This would allow you to have a fancy shophome where only the shopkeeper’s friends can enter the home but anyone can come into the business end.
Ability to set more than one “owner” for specific buildings and/or rooms would also be a good addition to the idea. Then you can have Hearthlings living together and sharing permissions priorities between each other for who can and can not be invited into their home. (IE if two 'lings A and B live together, and 'ling A likes 'ling C, but 'ling B doesn’t have an opinion on 'ling C, C can enter. However if A likes C, but B DISlikes C, C cannot enter.)
A Hearthling’s pet should also take up residence in the Hearthling’s home, if the Hearthling owns one, spending most of its cute fuzzy time inside where it’s safe from the elements like a real life pet. Maybe make a pet bed craftable by the Weaver that the pet will spend most of its time in happily.
Addition: Hearthlings who own a home should also spend most of their time in their home. If they’re a crafter who’s got work to do, of course they can do that wherever their crafting station is, but if they want to eat and sleep they should prioritize their home for these actions, as well as any idle time they might have. Perhaps give functionality to the Writing Desk and some other cosmetic household items the Hearthling can animate at.
Addition 2: I imagine this ability would take the shape of a UI selection similar to how you assign soldiers to squads in the Combat tab. Simply, a button to select from your list of Hearthlings to add to a building’s ownership tab from a clickable button that pops up whenever you have the building selected, or perhaps to make it less of a pain to access whenever you have any furniture in the building selected. (Easier to click a piece of furniture than to open the Build menu and click the building.)
The popup would suggest a Hearthling or a few based on beds in the building that are owned, and all buildings start with 0 ownership meaning every Hearthling can go in and use their facilities.