Mankind's wrath...that's perfect for even a post modern society. Reading Chrysostom it seems in this verse God is saving us from ourselves so to speak
But the reason most translations have 'of God' in italics is for the reason you state. But the translators were not applying chicanery to slip in a pet theology. I think you know these commissions have multiple denominations and also scholars from EO and RC traditions.
I believe the wrath "of God" was added because in Romans chapter 1 Paul established his argument of our condemnation before a Holy God based on His Wrath.
Romans 1:18 -
For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness
Therefore I think it fits here in chapter 5.
And I think it is not out of the question to consider John the Baptist confirming it is the wrath of God that abides in us.
John 3:36 -
He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him
I agree Chrysostom may have not used God's wrath specifically, but he did use substitution language.
Chrysostom, Homily on Galatians 3:3 (ACD, vol. 3, p. 108)
The people were liable to punishment since they had not fulfilled the whole Law. Christ satisfied a different curse, the one that says, “Cursed is everyone that is hanged on a tree.” Both the one who is hanged and the one who transgresses the Law are accursed. Christ, who was going to lift that curse, could not properly be made liable to it, yet he had to receive a curse. He received the curse instead of being liable to it, and through this he lifted the curse. Just as, when someone is condemned to death, another innocent person who chooses to die for him releases him from that punishment, so Christ also did.
In reality, the people were subject to another curse, which says, Cursed is every one that continues not in the things that are written in the book of the Law. Deuteronomy 27:26 To this curse, I say, people were subject, for no man had continued in, or was a keeper of, the whole Law; but Christ exchanged this curse for the other, Cursed is every one that hangs on a tree. As then both he who hanged on a tree, and he who transgresses the Law, is cursed, and as it was necessary for him who is about to relieve from a curse himself to be free from it, but to receive another instead of it, therefore Christ took upon Him such another, and thereby relieved us from the curse. It was like an innocent man's undertaking to die for another sentenced to death, and so rescuing him from punishment. For Christ took upon Him not the curse of transgression, but the other curse, in order to remove that of others. For, He had done no violence neither was any deceit in His mouth. Isaiah 53:9;1 Peter 2:22 And as by dying He rescued from death those who were dying, so by taking upon Himself the curse, He delivered them from it.
CHURCH FATHERS: Homily 3 on Galatians (Chrysostom)
CHURCH FATHERS: Homily 3 on Galatians (Chrysostom)
There are others to include Athanasius, Hilary and Cyril of Jerusalem using substitution language. And of course Augustine makes his view quite clear:
Augustine
“This, the catholic faith has known of the one and only mediator between God and man, the man Christ Jesus, who condescended to undergo death—that is, the penalty of sin—without sin, for us. As He alone became the Son of man, in order that we might become through Him sons of God, so He alone, on our behalf, undertook punishment without ill deservings, that we through Him might obtain grace without good deservings. Because as to us nothing good was due so to Him nothing bad was due. Therefore, commending His love to them to whom He was about to give undeserved life, He was willing to suffer for them an undeserved death.” (Against Two Letters of the Pelagians, Book 4, chap. 7)
CHURCH FATHERS: Against Two Letters of the Pelagians, Book IV (Augustine)
I know it is not your point but I've seen a few threads where posters claim substitution was a Reformation doctrine. Seems there was some early support for it, outside of the Holy Scriptures that is .