Eberlestock and Badlands both have designed in spots for carrying your hydration bladders and have different sizes of bladders available. For mountain hunting my personal favorites are the Eberlestock packs. You can check some of them out on my website, and there are other models available if you don't see exactly what you are looking for.
I really like the convenience of a hydration bladder over a water bottle. With a bladder the hose is always handy, and I drink from it frequently. Also, a bladder doesn't slosh around and make noise. With a water bottle in many packs it is necessary to take the pack off in order to take a drink, and I think that can lead to not drinking enough.
Proper hydration is very important, especially so in tough mountain country. I tend to go through a lot of water when I am moving and don't want to have to drop my pack to get at it. If you prefer the bottles, at least make sure the pack has a pocket on the belt so that it is readily available.