Banning champions that your team has selected

So sometimes people ban each other champs in champ select, riot has put a symbol over the selected champs, which is nice. However, it doesn't prevent it. Like people sometimes accidentally ban the champ that someone else wants to play. I find the most tilting thing is when someone puposely banns your champ just to be annoying (Or maybe they're trying to get you to dodge?). I don't know much about game design and such, but I really think it would help prevent trolls in champ select. Obviously there would probably be some problems with that system, but I think it would be a nice change.