I believe it would be a bad idea to limit zombies. Lets get real, we all know that humans always win the rounds, especially when they are vip, as there are weapons that are extremely overpowered. So players have found a way to win when they are zombies, which is to use sting zombie. ( i prefer my coffin zombie.) This makes humans have to be more "smart" (if I can say so) because this zombie is quite strong when its ability is activated. So players who normally wins the round easily have found this zombie (sting) a real reason for anger and sadness, just as those who don't have a high level feel sad and angry when they are killed instantly by players with strong weapons. Maybe it's easy to say "oh, but the weapons are limited, etc" but we all know the "damage" that two players with 2 rod weapons can do in the round. I don't think we should limit zombies as it is a way of encouraging them to try to kill humans. Furthermore, in a hypothetical situation in which 5 players have chosen their respective zombies (sting) and these 5 players are left afk, then we will know that there will be no chance for the zombies to win.
Now I'm saying something that is my opinion (and i could be wrong): The truth is that all players, especially high level ones, are crying because of the sting zombie and its ridiculously strong ability to remove all armor. So, maybe it deserves a rework, but I don't think they should limit zombies in general (knowing of course that everyone is more worried about the zombie sting.) Sorry to seem a little bold in these almost unanimous statements, but it's reality.