How about:
Re-define two blocks of our Key Items space (Has anyone ever filled this?) as job-specific inventory for gathering and crafting. One set for each job that pages in when in that job.

1. Gathering items automatically go into the related inventory.
2. Crafting materials are consumed from your main bag OR whichever crafting bag it's in.
3. Crafting results go into the crafting inventory

3. You can't store things in this new space if you're not in that job mode, but you can select it to transfer stuff out from any job, like the chocobo bag