Okay, if anyone watched TWD or played Telltales The Walking Dead season 4, then you might understand what I mean here. They don't have to be called "Whisperers" and don't have to act as such, but having a hostile faction of NPCs that can walk amongst zombies, lead them to you, or use them to attack your group would be cool. It could be a preset event instead of it happening whenever. Either or. The "Whisperers" or whatever you'll rename them to can be killed among those zombies, like they'll actually be in the herd blending in instead of just a swarm of walkers showing up. Killing and looting one could give valuable stuff, the skin suit they use to walk in herds, possibly weaponry, rarely a map to their base. You could find a whisper in smaller herds gathering up more zombies as they pass through.