Here are a few humble suggestions....
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Zombie Speed - i'm guessing "zombie_speed cvar for zombie speed" changes this? i always see them being very fast, when a human dies and turns, they enter rigamortis, causing muscles to be stiff. also they lack the coordination to even run. Zombies should not be faster than the Humans, if anything they should be slower. of course making them slow as hell wouldnt be fun, but making them super fast seems a bit unbelievable. I was trying to think of ways to slow them down to atleast human speed, but keep balance to the game. I was thinking maybe less knock back on the weapons. which i think is also a customizable feature. Also see Zombie Strength Below
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Turning - Its been suggested on here to add a delay. I totally agree. If a person gets "bit" he should lose a decent amount depending on the location of the "bite" then maybe every 5-10 seconds he loses a % or something. for example, he gets bit on the arm, he loses 20 hp left with 80hp. 10 seconds later he loses 20%hp and so on and so on until he dies and turns. Just as in a real zombie encounter, you know if u have been bit or not and its up to you to tell ur party of survivors. Do they let u live to be useful until ur close to fully turning, or do they take you out before u endanger the rest of the pack.
He are suggestions on dealing with the survivor in question. I don’t know if its at all possible, but could u make 1 person susceptible to Friendly Fire? I would suggest playing on full FF but there's too many jerk faces playing CS that would just be a kill joy. Another idea is if its possible to turn off player identification and when someone is bit, they are placed on the other team. But then he cant do much without FF.... but at least he can be killed easily by his peers
-or- make it so that FF is on, and only Headshots kill. it wouldn’t matter for the zombie because the bite is all it takes, and for the CT it would kind of be like FF is off, just gotta be more careful with ur aim. just like u should in real life!!!! =P
also, no healing. amputation has rarely every worked. Once ur bit, ur done. its up to you how u spend ur last few minutes as a human.
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zombie strength - i think the zombies are way to hard to kill. maybe its cuz im rusty as hell in CS. but how many headshots does it take to kill a zombie? i saw on here someone also suggested headshots only dmg zombies, which in reality, is the only way to kill a zombie. to balance this the idea, unlimited ammo should not be played, and maybe the zombie should be allowed 2-3 headshots. in a world where zombies roam the earth, supplies are limited. every bullet counts. Weapons ideal for human vs human warfare can be rendered useless or unefficient vs the army of the undead. i.e. para spamming (see Zombie Surival Guide pg. 41-42 Firearms.)
the zombie should in turn be slower. also, if a zombie is killed, he should respawn as a zombie rather than a human to simulate a bigger zombie horde. if a player dies as CT thru means other than "turning" (see above) he should be respawned as a zombie at spawn. Rounds would be longer and would be won by surviving the round. also no one would have to spend the round as a spectator since all death = more for the zombie team.
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map suggestions (just some ideas, i know its not the modders who create the maps but maybe map makers will see this as well)
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barricades - building barricades are important, but most barricades are penetrable eventually. the boarded up house lasted only so long until the undead got in. My memory is flakey.... did they get in because they broke down the door? or was Barbara stupid and opened the door herself.... but anyway, they always eventually get in. building an impenetrable barricade and sitting the rest of the round usually just wastes the remainder of the round. for example, i think its the junkyard map where everyone runs downstairs shoots everything in the basement making an impenetrable barricade then having coffee for 3 minutes. barricade building is fun, but can at times also make a map horrible. i feel a good barricade is a where it takes a good amount of zombies pressing e to knock it over, but also the humans have some chance of getting shots at them. it makes situations intense where a room has like 4 humans, and there's a struggle to keep the barricades up with the zombies working together. no room should ever be impenetrable. just very hard to get into.
also I feel the needs for having cheap rooms like a small vent, and everyone spamming paras and shotties to knock the zombies back by shooting thru each other wouldn’t need to exist with zombies being easier to kill (see zombie strength above ) instead of having a bunch of people cramming a vent or tube and spamming knockback's, it would be replaced with the slower zombie and skilled shooting. Which I think in turn would bring the same effect and be just as intense. like instead of 5 people in a vent, shooting paras and shotties thru each other to keep the zombies out, the same can be done with only 2 people, partially side by side, with headshots to slower paced zombies.
i think i had more on my mind, but i've been typing for a while and i cant think of it right now.
thanks for you time.