Yes, sooner or later all stands will get wet. I just used regular paint for my wrap, but it was more for aesthetics since it covers a powder coated metal stand.
Nothing wrong with leaving open as you are. In fact, if you have a sump it could look cool leaving it exposed. I like the look especially if you go hard plumbing. You could even add a plywood platform or tray for the sump to sit in/on.