If you're looking to be irreverent then this is certainly a start. Its not all about the gum chewing though, usually members that do this also are easily distracted or talking with their friends so its mostly an association game of things you do when you are not interested.
It depends how you chew it. I think is a matter of "manners" than anything else. I think if a member is chewing gum like a cow, then surely could be a distraction and considered to be irreverent (besides the manners issue).
Help when you are thirsty? When you are thirsty you drink water. Most chapels have a water fountain or water cooler of some sort. If you're worried about getting up during sacrament to drink then drink before or after! If you want fresh breath keep a mint in your mouth or some cloves. What else you got?
It bothers you if someone is chewing gum in church? Where are your thoughts during meetings? I can't ever remember noticing whether or not someone is chewing gum. Unless they are sitting by me and they are chewing very loudly which has never happened. I personally don't chew gum in church, but I wouldn't let it bother me if someone else does.
Ok, if this is irreverent, then I have to admit that I am guilty. My problem is having too many thoughts in my head, like having 5 TVs, 3 radios, and 4 conversations all at the same time. It makes it hard to concentrate on one speaker for a long period of time, even if I am very interested, and there is something about the methodic chewing that helps me calm Anxiety and focus. I never chew in an obvious or Obnoxious way, and since I've been doing this since grade school, where it WAS against the rules, I've gotten pretty good at not being noticed with it even when I'm talking. I agree that it is all in the way the person is doing it and, like so many other things, their general attitude. If they are smacking gum and blowing bubbles, then YEAH, that's not really reverent, but for those of us with too many thoughts or with anxiety issues, it helps us be more reverent.