Here's an interesting fact. All life on Earth had to be destroyed because the genetic flaw that allowed the Guyver effect was present in all forms of life.
But you've to ration that with what Matt said, we know a lot more about how the Guyver Unit works now to 20 years ago (thank you translators!!!!). The question would be how the balance would work.
it's a known fact that humans are one of the few species that are truly self aware. By that we mean the brain we have has gone beyond just survival mode which most creatures have. E.g. a road cuts through the rain forest. Some animals will never cross that road. They'll never figure it out. You could argue there are other animals on Earth that would over come something like this.
But the question would be without true self awareness would a Guyver Trex ever be not "Out of Control"?