From my understanding this game should be about adapting to the enemy. So at the beginning you can deal with enemy (let call him “A”) with what you have (let call it “Z”). Then enemy evolves (mutates) into “B” and you need to counter it with something else (name it “Y”) which you need to research. Then enemy mutates in “C”, and you need to develop “X”.
This means that “Y” will be to deal with “B” but not with “A” or “C”. “Z” won’t be good vs “B” or “C”, and “X” won’t be enough to deal with “A” or “B”. So all your updates and research won’t be really upgrades. They will only change your tactic. And I like idea that enemy could again go back to “A” so you will need to use your “Z” (starting weapons) so they won’t become obsolete even late in th game… 
But we will see how Snapshot Games will deal with that. They have many different types of damage, and they can have quite many different enemies (with this mutating body parts mechanic). It requires proper balancing but idea can work well.