What about another type that Can only be killed by a well-placed headshot, like if the bullet connects with the zombie's forehead, it dies (of course.) Though a zombie slightly faster than a normal player would be nice... Also, what about zombies with different behaviors or looks, like a zombie that spawned without legs, or a zombie that staggers as fast as a zombie can, sometimes tripping on air and falling flat on it's face, or a zombie that just sits on the ground and looks almost exactly like a player?
Random zombies that look like player's avatars is one of the reasons that the gamemode's zombies look so stupid. Please, don't do the same thing Rotondo did.