That's the point. Currently, the MW's reliance on NPC retainers is more of a liability than a benefit. Fixing it requires much more overhauls to game engine efficiency and server optimization. If I were in charge, this is what I would do;
Temporarily remove the ward aspect of the market ward system, but keep the retainers as storage and bazaar.
Have all buying and selling be done through the item search interface menu. (this should not take long since they don't have to deal with NPC overcrowding anymore)
Fix the underlying game engine and server problems so that the game can sustain a single area full of NPC retainers.
Reintroduce the "ward" concept and reintroduce retainer bazaars along with features such as custom stalls, advertising, etc.
Side note: you may want to read my market stall suggestions in my gil sink thread for more insight.
http://forum.square-enix.com/ffxiv/threads/11434-DevTalk-GIL-SINKS!-Ideas-to-Stabilize-the-Economy-and-Curb-Inflation