I really think Chuck Gardner's design is obviously the best for situations where no bounce is possible, and you want a single shoe-mountable light source. It has larger light-emitting surface area than most competitors, is cheap, and doesn't weight much. You could technically get a bigger softbox, but you could just as easily make an even bigger foam area and angle it correctly to spread the light. It doesn't waste light throwing it in directions where you can't get a secondary bounce, like Omnibounces, Fong tupperware etc. does. One should still be able to gel the flash to good effect. I think I'm going to make one soon!
For situations where you can bounce, I think bouncing is generally going to work better (or at least give softer light, which is usually the goal) just due to the ability to use a much bigger light source. Here I think the Joe Demb Flip-It has an edge, due to the fact you can change the forward fill/bounce ratio, and the fill is fairly soft.
In any event, sorry for the rought treatment, OP. I think your design is fine and it's fun to tinker. I see people making homemade diffusers for macro, which I'm getting into, and may use some of your ideas there. Seems like you might get more even light spread by adding a secondary diffusion panel inside the softbox, maybe made out of tissue paper.