A pre-note: I’m not saying any of this should be reflected in the game. It’s just me thinking about things. If afterwards I feel like something might be especially good in game I’ll comment on it at the end. This is mainly for discussion and/or sparking someone else to have an idea.
So I was thinking after reading some other posts that the zombies in this game are really oddly portrayed. Not badly. I’m mainly speaking on damage and the way they treat it. Zombies, like machines, are not phased by the damage they receive. The only way it will affect them, is the physical reaction to being hit/shot. Something like weight, strength, and structure vs impact. Now enough damage might take out/disable a limb or other part of the body. But bodies are pretty sturdy things. The organs inside them less so, but the body keeps together pretty well. It takes a LARGE amount of damage to totally destroy a human body. I’ve been wondering if there is a way to reflect this in game. This part is specifically pondering some things that are mechanic related based on a semi-realism, but not balance. Blunt weapons would do rather less damage to zombies with the exception of strong attacks against the head (crit). I’m wondering if we could use criticals to represent disabling strikes. Bladed weapons would have more chance of disabling crits. Severing tendons, destroying muscle, and straight amputation of limbs and digits. Piercing weapons would seem to be the worst of all worlds. They are designed to piercing into a body and hit critical organs and the like. Such weapons could be designed to work on zombies, but the chance of the weapon getting stuck and the difficulty of doing disabling damage would make them less so. Some of the weapons that have blades that are designed to help the weapon tear free would be better off. So what’s the point of piercing weapons you say? Piercing through armor and thick skin. A long spear would be good vs a single heavily armored zombie (firefighter anyone?). Guns would fall under piercing weapons to me. Tending to do damage to a localized area without doing the gross damage that would have more a chance of disabling a zombie.
Direct thoughts on this games mechanics:
I’ve heard some complaints about balance and guns. I’d say that adding things like damage resistances to various creatures would help some. Zombies would mostly have no armor, but be resistant to piercing and blunt weapons. Maybe raise their hp too to reflect that you can hack them to pieces, but it takes a bit of doing. 
Having creatures that are resistant to various types of weapons could encourage people to use multiple types of weapons.
Weapon uses:
Piercing: Good vs armored targets.
Slashing: Good vs zombies
Blunt: Good vs living targets
Also, another thought for balancing firearms… Players should be able to make black powder easily enough, but smokeless powder aka modern gunpowder is not easy at all to make.
PS: The pain part is how zombies and machines are not affected by pain. I forgot to mention directly in the above.