I think 1-2-3 new secret maps can do.
+ mutant randomization.
Maybe to make chaingun even less accurate and so very wasteful.
Also inserted new knight frames and new headshots for non-mutant SS and officer.
For mutant ones I was a bit lazy + I think mutant-blooded head to explode looks more horror-style and purple goo looks more slimy to us subconsciously, and also to add headshot variety. And because I was lazy. But if you insist...