Here is a good quote from Greek Orthodox theologian Khaled Anatolios on the vicarious humanity of Christ and Incarnation:
A helpful way to synthesize the argument of Against the Greeks—On the Incarnation and to integrate it with Athanasius’s later and more explicitly polemical work is to focus on the trintarian-christological-anthropological nexus that forms the guiding motif of the work: only the One who is true Image can renew humanity’s being according to the image (kat’ eikona). The trinitarian ground of this nexus is the immediate relation (though we do not find the later technical vocabulary of “relation” in this treatise) whereby the Son is the Image of the Father. The soteriological consequence of this immediacy is that the Son is uniquely able to grant direct and immediate access to the Father. The statement that humanity was created according to the Image is simultaneously anthropological and christological: to be created according to the Image is to be granted a participation in the one who is the true and full Image of the Father. When humanity lost its stability, which depended on remaining in the state of being according to the Image, the incarnate Word repaired the image of God in humanity by reuniting it with his own divine imaging of the Father. Jesus Christ is therefore both eternal divine Image and restored human image. The saving union of divine and human image in Christ is characterized by immediacy. One foundational principle of Athanasius’s theological vision is this stress on the continuity of immediate connections between God and humanity and a corresponding abhorrence of obstacles and opaque mediations. As perfect Image, the Son is immediately united to the Father and transparently reflects knowledge of the Father; anything short of this immediate and transparent relation would deconstruct our immediate connection with the Father through the Son from the divine side. Through his incarnation, the Son repairs our human participation in his imaging of the Father from within the human constitution; anything short of a full incarnation would leave humans disconnected from both Father and Son. Thus, incarnation and the full divinity of the Son are both integral to the immediacy of our contact with the Father. Far from indicating inferior divinity, the human life and death of Jesus Christ extend the efficacy of is divine imaging of the Father in the face of humanity’s loss of the state of being according to the image. It is a wonderful display of the loving-kindness that belongs to the divine nature as such, the philanthrōpia that is equally shared by Father and Son. [Khaled Anatolios,Retrieving Nicaea: The Development and Meaning of Trinitarian Doctrine,(Grand Rapids, Michigan: Baker Academic, 2011), 107-8.]
So we are images of the Image in the Son as we participate from His life for us. He is the Image of God, and the recreated image of the image that was originally created in the garden in Adam and Eve. So Christ was the human image of God whom Adam and Eve reflected as the image of the image first. It is only as this image is recreated and restored through the ‘firstborn status’ of the Son (Col. 1.15ff) that salvation and reconciliation is realized for us in Christ. This fits well with Thomas Torrance’s understanding of Theosis, and his ontological theory of the atonement; and something that is central to what Myk Habets and I consider to be the grist of evangelical Calvinist soteriology.