I also use a toolbox for storage, but I can definitely see an advantage to making a smaller version of your idea as a place to temporarily store pins while changing attachments.
LOL, I simply have a 'tool box' and rummage thru 'till I find what I need.
Mind U I Like the idea to retain pins when I change implements on a seasonal basis as most often I loose some.
Aren't magnets not just great?