Just today I was wondering how I am going to stuff my current Arduino project behind the dash in my car. I went looking through enclosures and always have to "guess" if my components will fit and hope I am steady with the drill and mounting hardware.
I know Adafruit has the ability to both build and source excellent enclosures and I am a happy owner of a Pi Box, Bone Box, and several of the proto plates. What would thrill me is something that had mounting for an Arduino on one side, a half-sized or tin-sized Perma Proto board on the other, and would snap together like a suitcase. It'd have about an inch in between which would be plenty of space for components and/or a shield and the wiring that would fold together. Ideally ABS, aluminum, or some other relatively-easy-to-drill material for attachments and wires.
The Pibow is an excellent idea, too. Users could made the enclosure thinner or thicker with different bolt sizes, swap solid plates for plates with cut-outs, and still have the perma-proto mount on one side and the Arduino on the other.
If some enterprising person with a laser cutter or 3D printer wants to try this, I'd buy 5 at $20 each. If there's enough of a market for it, maybe we can talk Adafruit into an original design.
*edit* I accidentally a word.
Open source projects: http://thoughtfix.com