I guarantee you won't be able ride chocobos in towns, at least not with rentals. Mounts in a city is one thing, but mounts in buildings is another. Since we'll only be dealing with rentals at first, it wouldn't make sense to be able to ride around town, get to a building, and then get off and have to run back to the stables if you want another chocobo. So if you want to go from point A to point B in a town, you'll have to first make a detour to the chocobo stables to grab a chocobo, ride it to where you want to be, get off, it runs away, and...yay? Doesn't seem like the most elegant implementation.