This is my first mod, which I wanted to share with everyone my success! I manage and finally edited the npcstat.engb!!
I only tried this on dead zone on ACT 1, and it worked. I doubt this will work with danger room sessions, cos I tried it there but they were normal enemies.
Download THE EPIC MOD (I'm not 100% sure it will work on extreme difficultly mod): mega.nz/#!QVwwCCjB!663t7rcUhK3NhIfIhG_A0JQLrF02gcted7N2LGICqqw (http://mega.nz/#!QVwwCCjB!663t7rcUhK3NhIfIhG_A0JQLrF02gcted7N2LGICqqw)
Hopefully more of my mods becomes successful and uploaded bug-free.
NOTE: Just played the mod while the file uploading. Any creature such as insects would not be mutated, this is completely unknown, however I can confirm that there will be more extra enemies as if they were failed to mutate successfully however they successfully added duplicated enemies. So any insects wouldn't be mutated. This is only confirmed only in a specific area, the underground tunnels. This may apply with other areas but as I said I did not test this fully.
EDIT: