I edited some files and achieved most of them disappearing but I'm not pursuing it further because Adeno has already completed it, they say, and should release it soon -

http://forums.undeadlabs.com/showthread.php?33990-George-Romero-Mod-(Experiment)/

I'd like to do this as well. Undeadlabs forum is currently down. Any suggestions? I have never understood the need for mutant zombies. Most films only have normal zombies and that's what everyone is used to. Why change our perception of zombies?

If you google George Romero Mod and find it on..i think like moddb or somesuch, one of the things you can turn on (by putting it in) is No specials.
One thing...you will STILL find screamers in infestations. Those simply cant be turned off as they are forced to spawn occasionally. Everything else has a chance, which if made 0, makes them never spawn.

The screamers are very connected to the infection mechanic. I've seen them head towards a house and soon the house was infected. So, you'd have to eliminate both.

Heya! Just a quick qeustion- I have the Romero Mod (saw it on PC Gamer, then dl'd it from ModDB) and I love it! But I don't see a "No Special" option. I see all the others, but not that one. Is it named something different? Thanks in advance.

In the George Romero mod's Readme File...
If you scroll down, in the normal story area, #25 is the Disable/Enable special zombies.
So its there..
But that number doesnt correspond to the files in the zip.

There doesnt seem to be a STAND ALONE of the 'no special zombies'
HOWEVER. If you read the file names in the zip, it does appear 2 times.
"MoreEnclavesNoSpecialZombies" & "MoreEnclavesExtraAmmoNoSpecialZombies"
So pick between one of those for it id say.

Did some further research into the OPs question. Here is what I have found.
In the enclave.xml file (Game/Libs/rts) (Which is one hell of a long file btw) are some very interesting lines of code.
They all read: Status.Enemy.Unlock_XXXXX
There are many of them, multiples for each. They all specify a type of special zombie.

THEORETICALLY: If you say deleted each single occurance of the LINE that has the "Status.Enemy.Unlock_Feral" (As an example) in it from the file, and used that. Technically no EVENT would ever 'unlock' the Feral to begin spawning.

If you noticed...certain..events ( i am not sure of which) seem to 'unlock' new enemies. This so if you removed that unlock code for a certain enemy time from EVERY place it appears. Poof..they never unlock, game never lets them spawn.

I haven't tried it myself, but that seems to be the key.

Since the guy that did Romero Mod didnt include the xml's in his mod, its not easy to figure this stuff out at times. Hope this is right, it looks right.

Also: The REASON that the Romero mod doesn't have this feature as a stand alone is because its in the enclave file. So he tried to bundle em up in sensible sets it seems but its weird that he didnt give a straight "No specials" option. Oh well.

Newest update of Romero's mod has No Special Zombies as it's own patch! Lovely. Seems it's not a story mode mod, just the DLC.