I hate discipline systems.
I'd never allow a yellow / red card system. If a user misbehaves, I am talking to him. When I ban him, I will tell him exactly why.
It's like the "dislike" link, if you like someone, you may click so, but dislike something, it's better to explain why.
I'd not put any ressources in that from the start. A perfect example for an addon from a third party, too.