It's not at all clear to me what you really gain from an f-stop backpack. It looks as though you still have to pack away the camera and lenses in the main compartment, just as you would with any other trekking backpack, so you still have to take off the backpack to access your gear. If they have a model that features a quick-access side compartment or something (like some LowePro bags have), then I'm not finding it on their website. It seems to me that the benefit you gain from these very expensive f-stop bags is pretty minimal, but maybe I'm missing something.
I just returned from a backpacking trip in the Dolomites. My husband and I are both photographers, and we had a lot of gear to schlepp between the two of us, in addition to all of the survival necessities for a three-day trip. We had him outfitted with a very large but comfortable trekking pack (probably about 75L capacity) and used a modular storage system of separate LowePro lens cases and pouches inside the backpack. Our tripods were in his bag too, each inside its own padded bag so that getting them in and out was relatively easy (when we slid them out, the bags stayed inside and held their space for them). I carried my usual camera backpack, which contained even more equipment. We had a great time and were both very comfortable with what we were carrying. I'm sure it helped a lot that the big trekking bag was a perfect fit, with great balance: I think that ought to be the starting point for purchasing any trekking backpack.