I dunno, this one seems relatively easy. As someone who once lugged a whole bunch of camera equipment (much wiser nowI carry a little digital Canon G10, $400, and nothing else), my solution is: A pack that carries well and carries what you need is paramount. Hit that bar, then retrofit for camera gear.
Because, as you say, there are no camera-friendly packs that cross over into the backpacking arena. Lowepros Super Trekker ($596) is big but strictly built for cameras. It doesnt even have a "gear" compartment.
I think a really good camera-toting pack would be the Gregory Whitney ($359). Its a classic, big internal-frame packnearly 6,000 cubic inches of capacity, fabulous suspension, ruggedly made. And...lots of ways to pack stuff, with multiple pockets and zippers.
For less money, REIs Mars pack ($200) is a little smaller but very similar in design. It also has multiple access points for stashing gear.
I always liked to add outside compartments, and would strap on after-market bits. Those are hard to find these days, but Arc'teryx still makes a good add-on external pocketthe Accessory Pocket ($30). It can be fitted to any compression straps and can hold a couple of short lenses or one longer telephoto. Osprey also makes a line of useful add-on pockets called DigiStows, which as the name implies are designed for todays digital gadgets. They run $15 to $25.