Right now people are using the backpack as a makeshift version of this... but it could be done so much better.
Here, I'll design the entire system for you...
Pressing f9 opens up your groups "Palette".
a thin board or slab on which an artist lays and mixes colors.
Contained within the palette is all the various ingredients and things that could be used as ingredients. Consider this a sort of "group inventory" as far as that goes.
At the top of the palette is various slots for you to put the things you use as tools. A hammer, a mortal and pestle, and so forth. You would place them in the slot and there they would stay until you moved them. They never swap out *into* the ingredient inventory.
To the right of the palette is a 4x4 box where you can mix and mingle things.
Here's a drawing in case I'm not being clear enough...
This would make life SO much easier for everyone involved. Hell make it an item you have to find, I don't care. MAKE IT DLC and sell it for a buck.
Just make this happen. Crafting is one of the most awesome aspects of this game and right now it's kind of a pain in the ass to manage. This would solve that problem in a flash.