I love crafting in this game. It has been done extremely well. In fact, its so good I often find my entire inventory is full of crafting materials...as well as my Retainers. I end up having to spend an inordinate amount of time trading back and forth with my Retainer to get the crafting mats I need to keep going.
I propose that SE give us the ability to craft items with ingredients stored in the Retainer's inventory. To make it a little more realistic, I would require that the Retainer actually be summoned so they can "assist" by "handing the materials over" when I need them.
Not only would this make crafting more efficient and fun by reducing non-value added inventory management annoyances but it would leave more of your character's inventory open for precious loot.