The irony is no one thus far as been able to defend PSA via Scripture, except that they change PSA to mean simply that Christ bore our sins and by His stripes we were healed.
You are right that nowhere in history does PSA crop up until the Reformation. Even Aquinas took pains to make sure his theory of Christ being punished did not become the heresy of God punishing His Son with the punishment for sin and out of anger. Unfortunately Calvin embraced it. And now, at least here, it is fairly widely accepted as tradition (it is assumed), although it remains a minority view world wide.
I believe the reason we see so many theories and interest cropping up (a renewed interest in the Eastern Orthodox view, Christus Victor, and Mennonite theology) within evangelical circles is more and more are seeing the flaw of PSA and seeking a more biblical approach. On one hand it leads to the foolish attempt to find PSA in antiquity. But on another hand it leads to people grasping at unsupportable doctrines (the Mennonite theory of non-violent atonement, for example).
I also believe the traditional approach the best. And, fortunately, it is not something that requires much reasoning out. All you have to do is read the Bible.
Quite so. All well-said.