Mk I is fine, but it's spine is really off. It looks too weak, and even in sci-fi concept I don't see how it would work. So spine definitely needs to be changed. As Darker7 said - Hard Driver mode should be the standart spine.
The creature looks too abstract. What kind of energy does it use? Does it have a digestive system like live beings, or uses other sourse of energy more like a machine? Can't see any eyes or ears either.
Better to launch a polished game with less content but without "Early Access" tag, cause it will turn people away after so many early access indie games have fucked up. And then make a regular content updates, even is they're small. Small frequent updates is much better than a big update once in...