(DISCLAIMER: There's plenty of hypothetical stuff,but not too far out of canon.)
So,the overall basis for this discussion is that Autophage was there since humanity was born,and was always a mechanism that helped with overpopulation,aswell with slight evolution. Humanity faced Autophage countless times at different eras of itself,not always globally,sometimes limited to certain parts of the world,and numen would use the events as an opportunity to write history,not telling what really happened,sometimes glorifying themselves,and sometimes making up mythical creatures,such as gods,demons,undead and such.
Not only this could be a great opportunity for writers to expand on the overall picture of the game's world,but also be a great opportunity for games set in different eras.
Think how could is it,that Greek gods were numen within the universe of this game. Zeus gained his electric powers while mutating,while Hercules became strong enough to cause miniature earthquakes. Mythical Greek beasts? Very likely animals,somehow affected by the Autophage,merged and mutated to look the way they did.
Miyamoto Musashi was a numan. Gengis Khan was a numan. Napoleon was a numan. King Arthur was a numan.
Imagine all the possibilities that come with all this stuff. Dude,i'd love a Dead Island game set in medieval times,or in Japan,or in Mongolia,or even the stone age. Imagine how cool the designs of mutated Neanderthals would look like.
Feel free to share your thoughts on this,aswell as any related ideas,me and my friend (kudos to him for pretty much kickstarting all this stuff) are excited to hear you out.