I admit, that聮s a tough one. The best pure camera backpacks are from Lowepro, such as their Super Trekker AW II ($390 street price; www.lowepro.com). It聮s big, holds a ton of camera gear, and puts everything at your fingertips. But it聮s really not a pack that聮s designed to do much else except carry cameras. There really isn聮t a convenient place for so much as a jacket, let alone a hydration unit. Or lunch! And it sounds as if you聮re really doing some backcountry photography, not just schlepping around camera gear.
Osprey Atmost 65

So, I聮d recommend you keep adapting non-photo backpacks to your ends. Osprey聮s 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 you聮ll need to buy your own bladder. I also like Marmot聮s Bridger ($249; www.marmot.com), which is adapted from the Dana Designs line Marmot purchased. It聮s 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. You聮d 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 you聮ll get along just fine.
Get more advice from the Gear Guy as he picks this season聮s top gifts in You聮ll probably find a few things to put on your own wish list, too.