the risks outweigh the benefits. Water would definitely splash up onto the connectors. If the salt creep is building up on the splash guard, then it will probably build up on the bulbs too. As for heat dispersion, it would probably go into the water quicker. The splash guard helps keep the heat in the hood where the fans will blow it out. It will look a little opaque after a while, its expected to get scratched. If you're worried about it, you can snag a new one. I think nano tuners or nano customs might sell them. But I would recommend leaving it on. you don't want to short out your bulbs and blow the ballasts, or even worse, start a fire.
If you want an easy water change without removing the hood, get yourself 2 maxi jets (1200), put in the tank, and one in your new salt mix reservoir. pump some water out, then pump fresh salt water back in. It works for me.