That's pretty stupid suggestion. A ban shouldn't be handled by his reputation. It should be handled by whether he breaks the rules set here. You could get "Repfucked" and have -200 rep and still be an HQ person.
I am not sure if this is a great idea. Having a negative reputation doesn't mean, the person needs to be banned. It just means that people on the forum doesn't like that person
I dont think this is a good idea, people will just gang up or multiaccount to get people banned. And rep is just how people feel about you, 10 people could hate you but you could still be a HQ member.