I admit, thats a tough one. The best pure camera backpacks are from Lowepro, such as their Super Trekker AW II ($390 street price; www.lowepro.com). Its big, holds a ton of camera gear, and puts everything at your fingertips. But its really not a pack thats designed to do much else except carry cameras. There really isnt a convenient place for so much as a jacket, let alone a hydration unit. Or lunch! And it sounds as if youre really doing some backcountry photography, not just schlepping around camera gear.
So, Id recommend you keep adapting non-photo backpacks to your ends. Ospreys Atmost 65 ($229; www.ospreypacks.com) holds a lot (4,000 cubic inches of capacity), a great suspension, and outside pockets for camera gear for those things you want to keep handy. Add to it some REI Accessory Pockets ($15; www.rei.com) for extra lenses and other stuff. The Atmos is hydration compatible, with a pocket for a bladder and slots for the tubes, but youll need to buy your own bladder. I also like Marmots Bridger ($249; www.marmot.com), which is adapted from the Dana Designs line Marmot purchased. Its a touch smaller than the Osprey, and has two roomy vertical pockets on the outside that are perfect for lenses. Tripods tie on easily, too. Youd have to simply slip in a hydration bladder, such as an MSR DromLite ($25 for 2-liter model; www.msrcorp.com). The Bridger goes for $250.
Not a perfect solution, I admit. But I think with some planning and a few after-market additions youll get along just fine.
Get more advice from the Gear Guy as he picks this seasons top gifts in Away.coms Holiday Gift Guide. Youll probably find a few things to put on your own wish list, too.