Well, I think it's very enterprising, and you should be pleased with it.
For closing it you could consider Velcro. Probably ideal.
My only worry is that the points of the picks are where you fold the top part down over, and could start to make holes. I wonder if you could do something to encourage the fold to be slightly higher than the pick ends,such as sewing something thicker inside the bottom half to force a fold at a certain height, and/or add a re-enforcing strip of something tough along the part where the tips will press.
Still, only you can tell what is needed, if anything. The good thing compared to the case my SO MPXS-14 set came in, is that you can see all your picks and just lift out the one you want. I have to tip all mine out on the floor and then search through the pile.
