These are all great suggestions. I really like the ideas you have for the Retainer Equipment issues. In addition to your suggestion for the ability to remember the previously listed price you posted on that item I'd like to add the following ideas for your suggestions.

-Add the ability to post multiple listings of an item at a set stack size in one action
-Add the current listings and recent transactions into the "create listing" interface. The need to click a button to view other listings and sales history is just annoying (a lovely feature to view that info, but poorly displayed in nested windows). Just make that all included in the listing window when the player is setting their price for their item.
-Ability to view/post Player and Retainer Inventories during the item listing process. These options shouldn't be separated.

The interface and quality of life features needs to evolve for the sake of our sanity!