More O rings! (especially Brain Bag)
My brain bag has just one O ring, inside the little pocket on top on the outside. I'd like more.
For starters, I'd like one at the top of each of the long tall side pockets, that's where I'd like to keep my keys.
Also, a few in the main pocket, at the top, could be useful.
And lastly, you should point out that the Snake Charmer is designed to sit on top of your stuff, in the curved top of the Brain Bag (and presumably other backpacks). I ordered mine on a whim (I wanted to get some sort of minor bag). Once I had both in my hands, it was clear why the Snake Charmer was shaped that way.