Dude, I think that is a great idea. I wear a Camelback and a Fuel Belt during my spin class. It really comes in handy when I bust my ass and do a 5 minute transition run on the treadmill at 6.0 mph afterwards. I once saw a guy get out of the saddle in a spin class and because of dehydration, passed out and fell off the bike and broke his wrist. So, not only do I wear a Camelback and a Fuel Belt, but I tape my wrists too. You can never be too safe. You are right, people are thirsty in that class and I let them have a drink out of my Camelback as long as they don’t put their lips on the tube.
Don’t let the people saying mean things on here bother you. There are enough that people are actually quitting!