Retainers as they are presently, are 'useable', but the way we interact with them could be greatly improved.
First off, please add the option to manage retainer bazaars from the Inventory management screen. (Have the option to change from retainer and player bazaar, to retainer inventory and retainer bazaar contents.)
Additionally, add the option to swap retainers without having to cancel out every menu and restart the retainer process anew. If anything this would the most important off this list. The time people would need to spend dealing with retainers could be greatly reduced, and make accidentally summoning the wrong retainer or needing to shift inventory from one to another MUCH quicker.
The option to move equipped gear to the retainer would be a useful feature for those of us who forget to un-equip a piece, have to close everything out, un-equip, restart the summon retainer menu, and put the item in. It would also be nice if we could just equip/unequip gear from our inventory in the first place, the game should know where my sword or helmet goes.
Anyone have any other ideas on how using the Retainers could be made easier/quicker?