Gotta reopen this. I'm itching to reboot GW, and actually be able to play something!
So, you were talking about races? Races are key to GW, and that's a big design challenge that's significanly different from 3.5. In 3.5, the race takes a back seat to the class, tweaking it more than anything. In GW, though, I would argue that the reverse is true--the race defines you more than the class.
Just as a brainstorm, I'm thinking of dividing races into a few categories, based on how far mutated you are: Pure Strain, Stable Race, Mutant.
Pure Strain creatures are creatures that have not mutated and are hardier as a result. Humans are about the only playable PC race out of Pure Strain species (but hey, I'm not judging, I'm sure someone wants to play a monkey or something).
Stable Races are mutant races that have stabilized their mutations. Dabbers, Badders, Hissers, and the like. They can be mutated by radiation, but not much. They also have full communities of others of their race.
Mutants include everything else. They have the most variation in their mutations, can be plants or animals or people, and typically do not have large communities. Mutants might have one village, and that's it. They can quickly mutate in the face of radiation.
How much mechanics do we need to define the differences between human, animal, and plant mutants? If we all agree that you can walk around, pick things up, and talk, does the rest change?