The hydration chamber is a good idea. I'm convinced shifting MC is one of the biggest unseen causes of bow issues, at least in the long term. Hydration Chambers let you keep the bow at it's original performance easier.
You may have considered these options but in your part of the country hickory is king. It will shrug off all but the worst MC abuse and shoot all the faster for it. If you want to get really evil with your design you can do boo/hickory or sinew/tempered hickory (which will shrug off virtually all MC issues, or sinew/juniper etc. Boo/Osage will also be good. White Oak is also worth a shot. I've gotten away with murder with it. Avoid yew, red cedar and other such woods. Red oak is also sort of an iffy one in those conditions but that largely depends on the grade you get. I once found a dark red board of red oak that felt as least as dense and heavy as an Osage board of similar dimensions. Still kicking myself that I didn't buy it.
Do you have any other bows planned? It's hard to build just one.