Way back in 2012 we started with a flesh+metal design approach in which the X-Morph would eat the humans. They were supposed to be a carnivorous alien race that would mutate and assimilate human technology. Humans would be eaten like health pickups and enemy vehicle parts would serve as upgrade parts.
Unfortunately we couldn't shake the "Zerg" feeling throughout development and we decided to go for a pure tech/metallic apraoch. In the end we dropped the flesh/metal design in favor of a more metallic approach. We'll try to shed more light on our design process in the coming days. Let us know if you want to know more about this story.