This is one of my ideas so give me some credit if you take it.

It would use the skeletons and zombies from the base game and give them weapons that shoot a lot of lead and have little recoil and damage. I was thinking about adding some armor to some of the zombies or give them jetpacks so they can move around. And modify the rocket pod to hold a LOT of bodies.

I'm not much of a modder myself, so this might never happen if you want me to do it.