So, I’ve been thinking, when a town hall is built, that makes it so no other town can be founded in the, up to, eight tiles that surround it but that got me to wondering…why couldn’t the town build more useful buildings in those tiles, the kind of buildings that require the presence of a town hall. This would allow for things like the tile with the town hall to be the main source of faith and trade, while the surrounding tiles could be used for farms and resource production as well as more quiet homes outside of the busy main city. The finer details of this could certainly be worked out by future commenters but this is the general premise that I had in mind.
The examples you give of what these side tiles would be used for in your suggestion (farms and homes) are already possible, and you don’t need town hall based buildings to make them. You can make them without a town hall right now.
Having the other buildings available on these outer tiles that normally require a town hall, like watch towers, markets, banks, etc, would be way too over powered and would undermine the central tiles - why go there when I have everything I want here?
Also, tiles are separate large swaths of land that are many hours apart, so it would not make much sense to treat a tile next to the main one is part of the town itself. Those outer tiles are the outskirts of town.
There is already a suggestion up making guards an exception for this that you may be interested in: Suggestion - Guard Outposts
So what you’re asking is already possible, aside from the powerful buildings. You just have to move your characters on these outskirts and make your homestead.