However, the more advanced Terminators had to evolve from something...don't ya think?
No, I don't think they had to evolve from something. Think of the circular time concept.
-the Terminator arrives in 1984
-Cyberdyne finds the Endo remains and chip in their factory
-Cyberdyne builds machines (God knows what kind) and the 600 series infiltration units, aka the Terminators, end up exactly like the 800s, but with rubber skin since cyborg technology isn't developed by Skynet until the end of the war according to what Kyle says from his 2029 perspective, "...but these are new; they look human." But remember that Arnold is "Cyberdyne Systems Model 101". That means they made it before the war, or it would be called Skynet Model 101 or have no designation at all.
-Skynet deploys the 600s near the end of the war--according to what Kyle says, "Terminators are the newest; the worst,"--to infiltrate and target the leaders of the growing resistance that is becoming an increasing threat. Until humans started to rise again from the holes they'd been hiding in, taught to fight back by John Connor, Terminators were of no practical use and would have remained dormant or unmade in the automated factories until Skynet had a need for them.
-the 600s prove to be easily spotted with the unconvincing rubber skin (not because they are huge and primitive by comparison).
-Skynet develops cybernetic flesh (the only difference between 600s and 800s mentioned by Kyle Reese in T1)
to create the 800 series cyborgs
-A T-800 Cyberdyne Systems Model 101 is sent back to 1984
-The time loop starts again.
No evolving. Cyberdyne basically had the blueprints and ability to make the rubber-skinned 600s before Judgement Day, but not the technology later developed by Skynet to make the 800 cyborgs. If Cyberdyne built Skynet for Norad, it is fair to assume that they may also have had the artificial soldier (600s) in the works for some branch of the military as well. And the Model 101 could and should have existed for both rubber and cybrorg skin version if Cyberdyne is credited with designing it.
Drake would be proud.
