I really like this idea, because running for 5 kilometer being chased by zombie indefinitely except if the zombie decide to follow another player. Slow zombie only head shot and they can quick kill you, but don't run around you like a crazy dog to finally come slowly to fight you. A melee system could be good too, because when you are out of ammo the only way you are is to find ammo in a village full of zombie... Its hard and generally we are fucked.