It should be noted that this question is asked by one who does not accept (so far) the proposition that God's actions (if such an entity exists) are (or even should be) perfect and so I would ask that you avoid this kind of response...more I'm asking you to 'sell' this concept to a disinterested buyer! (so to speak)
I am not interested in selling anything, but I will offer an alternative explanation, so that you can see that it is possible to move on in 2,000 years.
There is something called the Unequal Exchange, to explain the Incarnation without recourse to all that talk of sin and punishment. In essence we have a God who is immortal and perfect, who creates a world that is finite and contains imperfection. He creates mankind out of love, because he delights in creation, and in relationship.
(I know you said not to mention perfection, but quite frankly, who would want a God of imperfection?
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But what he has not created is any earthly immortal creature, who can share eternity with him. So in order to allow us to access immortality, he comes to share our mortality first. He becomes man, and at the moment when he assumes human life, that presupposes that he will one day die. So the Incarnation is important from the first moment of Christ's conception to the moment of his death; it is all equally valid and equally important. He shows us how a perfect man would live, how he would speak and act, and what he would do. He gives us the perfect example for our lives, and then he lays down his life, willingly.
We are so used to this idea that we forget how radical it is. The Moslems have not lost sight of this radicalism; they cannot get their heads around God dying, and yet we accept it without thinking every day of our lives.
God became man, then laid down his life for us. Then he says, all you have to do in order to share in my immortality is to believe in my Son, who died for you. When we choose to do so, we become co-heirs with Christ, and we inherit eternal life. Not because of anything we are or do, but because of who Christ is.
This has really very little, if anything, to do with sin, everything to do with relationship and love. The parallel is our own lives with our parents or children. A relationship built on fear, punishment and constant rebuke is not healthy, but seriously dysfunctional. Some Christians have this same dysfunctional relationship with God, because they do not know anything else. But it is not who God really is.
Try that one for size. But whether you buy or not is up to you.