Constantinople is all fine and dandy, but most people in the outer grids don't have enough agi to travel there. Regional marketplaces suit them better. Those still don't help people that aren't living in one of the villages connected via crossroads to such markets.
Enter charterstone. Instead of using it as a spawn point (that's not really working out), use it as a fast travel point. Authority figures of a village should be able to grant right to use their charterstone to any outsider (all villagers have it by default). This right should be revokable, of course.
Anyway, this also allows for a limited degree of security, since only select people will be able to come to the marketplace. The increased sense of safety may even result in people actually using vending stalls. And yes, I'm well-aware that fast travel is going to be scrapped, but this seems like a simple feature and would serve well in the meantime.