While haven and hearth representation and relations between players mostly works akin to wild west, together with allegiance to the settlement/kingdom, I always felt lack of governmental documents that might play an important role in established settlements.
Add documents to the game, that will allow hearthling to perform certain granted actions in villages, despite the fact whether one belong to the village or not. I know that there is personal claim system that always overrides village, but it's too limited and dependent on land.
It's not something that should be done with clear intention of use, it's rather expand variety of opportunities that can be opted to use by players, so players could invent a best usage of the mechanic. Just like bill of possession, which while totally useless by all means for regular village is indispensable in any market.
One could only assume how can it change meta: projects even larger than whatever bay, automated citizenship systems in open villages, roman empire, feudalism?