Keep merchants at the station, in rotation.

[IshmaelNemo]

I would love this. It could be as simple as the merchant exiting their shuttle and moving somewhere a little more convenient for the duration of their time docked with the station.

It would be really cool if they stayed around the public market to sell their wares (but I do like the barzaar idea). Maybe add an all-purpose  delivery pad (like on merchant shuttles) to the market for whatever traders stop by?