Other games have similar options to this, but it would be nice to actually while away the hours actively selling to the public, instead of praying that one item sells on the MB.

Even if it's not completely free of a 'tax' but incredibly reduced compared to the MB (like 1% on the total session takings) it will still prove to be an incredible opportunity for players who want to further develop mercantile ideals. As for any beginning quests or such, each major city has a master of the markets which beginners get a quest from to understand the markets so the groundwork is laid already to use them.

The only downside I can see is the rules regarding placement of the stalls, because unless it's properly managed, players will not only quickly run out of room, but it may obstruct other players from using the MB or other merchants in the area.