The wards, and the retainers clutter what could be an even more streamlined system. Having everything be menu based, from an NPC in town is easier to understand for new people, and it is easier to manage for everyone else. Trying to keep retainers in such a system would only serve to unnecessarily complicate it. That is why I think that they should be two totally different systems.
To me, ideally it would be like this:
If you feel like browsing for goods, you can go to the market wards and browse retainers, similar to "rolanberry market" in XI. If you need items now, or are regearing a class, you would have the Auction House, where you could instantly search for, and purchase the items that you need, or list the items that you want to sell whenever you want to sell them.