And how exactly are you going to logically implement such “non-stacking”? Is your survivor suit’s armor going to suddenly become thinner just because you installed subdermal armor or grew scales?
Why? Why you are always defaulting to “let’s make it impossible”? Why not “let’s make it possible, but tricky, requiring tools, skills, resouces and time”. Do you know, what you are going to get by “this is impossible” approach? Too Awesome To Use - that what.
That would be against the lore. Mutations are XE037-created, and XE037 seems to be perfectly fine with bionics, if bio-operators, shocker, shocker hulk and technician zombies are any indication.
But it is illogical. New corpses for reanimation are not going to to simply appear from nowhere. If you cleared some zone from zeds - it should stay clear. Evolution of zeds where they were not cleared, however…
For what? To collectively die horribly as they are not adapted to our dimension? What purpose can they have in the world that is deadly inhospitable towards them?
And this seems to be more along the lines “mutate or die”. How would carnivorous characters without “Intestinal Fortitude” survive this?