I've got a new Zimmerbuilt pack coming in the mail, here are the pics if you're interested. It has the usual U-frame that Chris has been using. The dimensions are a little bigger than what you have in your drawing but pretty close. 12" wide, 8" deep, and about 32" in height. I think the way the pack is packed in the pics and the removable side pockets make it look stouter and deeper than it is in reality. Also, I asked for the angled bottom as you can see, like his ZB4 line of packs (look at Gear Deals page). This bottom is apparently stronger and more water resistant because there are less seams. Also, I hate it when a pack sags below the buttocks, it feels much better with the weight sitting above it IME. The two side pockets are removable and can be made into a lid, fanny packs or chest pockets depending. I haven't tried the design yet though so it's all in my head. I don't like things hanging on the outside of my pack in general hence the lack of permanent outer mesh pockets and the like. I have no problem stopping and taking my pack off for a drink of water. Fabric is Xpac everywhere. Similar but obviously different than what you are proposing.
Hope this helps in your endeavor, it was a lot of fun working with Chris on the design. He will essentially build anything you ask him to, within reason. Great guy though, and excellent communication/customer service.
weight is 29 oz. including side pockets, w/out I have not weighed it
Edit: I guess it's kind of hard to see, but there are 3 side compression straps on each side, roughly in the same location as you have on your drawing. The side pockets have channels on the back that receive the webbing and secure them on the sides.