having played this game for over 300hrs, you get boored with the same monsters/zombies what ever you want to call them, i was thinking that maybe they should have fresh material.
I.e you buy a scar, but it can be upgraded at a cost so you have higher magazine rounds, or a higher scope, different types of bullets, but each weapons have there own upgrades. also perks can have upgradable items such a medic, once you get into a level you buy faster heal, or can run quicker, faster reload. the amount of content that can be included. is loads.
It doesn't matter how many things you list that would be nice to have purely because its something new. TWI is a small company and the balance is already in ruins without adding even more things. Once you start to add variants or upgrades of weapons things are just going to spiral downwards badly and they simply don't have the time, or reason to update it with any of that. If anything like that would be coming it would be in KF2.
It may not be competitive player vs player, but coop without balance is no less tedious. The game used to need you to team up to take down Fleshpounds, now that duty is simply deferred to the resident Sharpshooter who can 1 shot it without even trying.
Sure most of them are melee attackers but you may aswell try saying the Special Infected from L4D aren't diverse... slow tanks puking acid, dashing attackers, slow grabbing cannon fodder, ankle biters, stealth attacks, PBAoE, ranged AoE... etc


