OK; so that's the rationale! Or at least one of them.
I remembered years ago seeing one of the cult books condemning the Jehovah's Witnesses for saying Adam was lost (in addition to the rest of their doctrines), and the argument seemed to be that their wearing of the animal cloths God provided for them constituted their "receiving of God's saving grace" (i.e. animals were "sacrificed" to make the cloths to cover their "nakedness").
What you're saying is different from that, and I had never heard that idea before.
Perhaps it seems ironic that he is the one whose sin brought eternal death to everyone else, but that he himself would get off scott free without even having to repent like everyone else.
But he didn't get off scott free. His life was drastically changed. He was chased out of the garden of Eden. He was denied access to the Tree of Life, which presumably could have given him eternal life on this earth. Now, he had to toil and work with the sweat of his brow that the earth would bring forth its fruit. His wife would bear children in pain. He would have the rule over her. He would have the responsibility to take care of the earth, to rule and have dominion over it; whereas before that time it was friendly and there was little he had to do, now it had become more of a hostile environment.
From this point onward salvation could only be obtained through faith sacrificial blood sacrifice as God directed.
There was repentance. God himself sacrificed the first animal; the first bloody sacrifice on behalf of Adam and Eve. This had nothing to do with climate, warmth, nakedness, etc. It was the fact that blood had to be shed for their sin. Inherent in this sacrifice was their repentance. If you study the names of their subsequent children you find the hope of a coming Messiah. Even in the midst of the Fall, in the words directed to Eve (Gen.3:15) we have the first promise of a Messiah.
Isn't there a difference between him being a child of God by creation, as opposed to spiritually? That's a similar assumption as the Israelites made regarding their physical lineage.
God's promise was two-fold:
"Thou shalt surely die."
1. He immediately died spiritually.
2. He died physically hundreds of years after that.
Death means separation. When he died spiritually he was spiritually separated from God. What brought him back into fellowship with God, was that animal that was sacrificed by God himself.
"Without the shedding of blood there is no remission of sins."
Adam was never lost. He never had anything to lose except his relationship with God which comes through disobedience. Every child loses this same fellowship with their parents through disobedience. Through correction and repentance it is restored. Often there are consequences involved, as there was for Adam, and as we have seen, for the entire human race.
