I think it would be a grave mistake to make PvP less of a focus. Adding more mechanics is fun, but ultiamtely this is a pvp focused game.
But experience has shown that that’s not true. Even with more challenging zombie hordes, killing a player is fun and takes just a few shots. This is something that is true in all zombie media as well, once players find out how to deal effectively with zombies, guns will be used against other players. Your idea sounds nice on paper, but really just won’t work, since especially with the loot tiering it will take less shots to kill someone, since they’ll have jack shit to shoot back, so you can afford to be more risky.