So my plan is to approach it the same way that I've constructed backpacks so far: start with the smallest pocket on the front and go from there. I figure there's no point in making pattern pieces for every bit of it until I see how the cargo pocket goes.
I'm going to make two backpacks at once. I'll do every piece with cheap fabric first (a hospital blanket), and once it's tested good, I'll repeat it with nicer fabric (hot pink polka dots on black -- thin canvas).
I'm going to be making the pattern pieces in the Libre Office version of PowerPoint and I'll upload each of the files after I've tested them.