Here is a link to a way bigger scale of what you are doing. The animals being kept are alittle different but it may give you some ideas.
http://www.monsterfishkeepers.com/forums/showthread.php?329022-1700-Gallon-Stingray-River
I don’t know much about snakes but keeping many different aquariums, I would make sure to make the tank easily accessible for maintenance reasons. I’m sure you have thought of this but you don’t want to have to climb into that enclosure every time you need to clean the tank. Maybe make an access door in the back or side, but you would have to take the waterfall into consideration as well. I’ll do some thinking on a waterproof entry and get back to you...
Anyways, this sounds like an awesome idea. Please log your build here if you have the time. We would love to follow along.
That is the exact thread I was thinking of, I remember it standing out in my mind as a kicka$$ tank and exactly what I would do if I could convince the wife to allow me to pawn off the kids on some materials to build it LOL