I think you should get some xp if you win a round of infection. Now you don't get xp until your the ONLY ONE alive. Then you have to suicide, which you cant do with 25 zombies chasing you. I think as a reward you get xp if you win. Also there should be a way to become a starter zombie like /startzombie but only 3 people can do it. If 0, 1, or 2 people do it it will just randomly pick.
