First, something like this would definitely need to have valid reports trigger the punishment. Just receiving reports is not good enough as they could very easily be false reports. So, receiving enough valid reports would trigger a punishment. The thing is, though, this already happens, it just isn't as fast as most people would like in most cases, for intentionally feeding that is.
When it comes to intentionally feeding, or trolling in other ways, Riot wants to be absolutely sure that the player in question really is intentionally feeding and not just having a bad game so they don't punish any innocent players. Because of this, the process of punishing intentional feeders tends to take longer, causing some players to get away with it a lot longer than they should, but I can tell you that people do get punished for intentionally feeding.
As far as IP bans, they are fairly ineffective. For one, it's not that difficult to change your IP address. Many routers change their IP address simply by turning them off then on again, so it's pretty simple to avoid IP bans. However, even if it weren't, IP bans come with collateral damage. Years ago Riot actually did issue IP bans, but one time they banned the IP of a college dorm, causing several innocent players to be banned for the actions of one.
miss me with that ban shit [sg-ezreal]
