I think what they do now is more than enough. I know that for counter strike, for example, will ban your account. so the player has to buy another game in order to play in the non-cheat servers.
If they did begin to ban using the IP address then i would assume there will be alot of angry customers. My cuzin cheated using my account and got me banned. Forcing me to buy a new game. If they had banned my Ip then i would of hd no way of playing again. lol