However, freedom to deviate creates diversity (among possibly other advantageous traits) and over-adaptation to one's environment can cause a species to "put all its eggs in one basket" and eventually become extinct.

You seem to be ascribing magical properties to one source of randomness. What special 'diversity' is being caused by 'free will' that one couldn't get by, say, cutting back a little bit on DNA repair and error-checking mechanisms? Or by amplifying thermal noise? Or by epileptic fits?

(Bonus points: energy and resource savings. Free will and no DNA error checking, two great flavors that go great together!)