An idea that happened in the openbeta discord channel, posted here for further discussion/later reference.
Being able to upgrade the town hall, turning the town into a capital city. This would take a lot of resources and labor. It could increase limits of things like tamed animals and utility buildings, but there could only be a limited amount of them in the world. This would allow large amounts of people who want to live together to do this, and could cause interesting IG conflicts.
It should also be possible to remove the capital status from a city, forcibly or otherwise, allowing other towns to upgrade and take over as a capital.