The Villain EX is NOT waterproof. It has foam floatation, so it won't sink, but it can get water in it. It has a waterproof box for the electronics (not batteries), but water can still get in if you flip it and it just sits there for a while.
Here is what happens when you flip it.
The Titans can handle the voltage, the higher turn ones in your new one will handle it better probably, but their life will be shorter than if you just ran the recommended voltage.
I read somewhere that EVX's have different voltage limitations from ESC to ESC, and if you put too much voltage to it, it simply won't drive the motors. Then you can drop a cell or two and it works just fine. I heard of someone on the Traxxas board, rupert I think, who had one that could do up to 18 cells:036:. I haven't tested my EVX's voltage limit, so I don't know if it will do more than 7 cells. My packs would usually read about 9 volts when fully charged, so mine should be good for up to 18 volts, I hope.