It's like saying I am a doctor because my brother-in-law is a doctor. It's a very odd substitution theory where nothing is being substituted. Second, it begs the question, "Was the crucifixion unnecessary?"
To answer the second bit first... the crucifixion was necessary so that God could taste death for every man, and by doing so, defeat the sting of death by his divine power by rising from the grave. And by his defeat-and-victory over the grave, he also defeated the Satanic powers of this world, the same powers that crucified him. Our flesh is in heaven, at the right hand of the Father, above all those earthly powers.
To answer the first... it's not a fair analogy, because in our glorification we also share in the same glory of God. We become like God, even if dimly so. But nonetheless, people will be able to see the same glory clothing us that they see in God. We become God not by melding with his nature, but by "irradiation" of his grace and glory, just like putting a piece of metal into a fire.
The Bible clearly links Christ's death and resurrection to salvation - Isaiah 53:5, 1 Corinthians 15, etc.
Of course, but we need not think of salvation in strictly juridical terms, as a law-court transaction.
I also want to add, I very much appreciate the external nature of the Word in Lutheran theology and practice, that makes Lutheran sacramentalism truly sacramental in the same way that the Orthodox understand the sacraments- they are objectively given for us. Calvin did not understand sacraments in that way, and so departs in many ways from the catholic consensus, though Augustine seems to have had more of that view of the sacraments (that they were signs pointing elsewhere, to heaven etc.).
It's one of the reasons I've sought out a Lutheran church, the Episcopal parish I was attending had a mixed bag of preachers, sometimes with a very low view of the sacraments. They were "reminders", which is pretty much what the Calvinist view devolved into. I very much believe our faith should rest on something external to us, even while I acknowledge a mystical dimension to faith inwardly, our faith cannot rest on our own spiritual experiences. The spiritual experiences help make that faith alive, but they do not justify us. I completely reject the "conversionism" found in many radical pietist churches, even though I acknowledge conversion is often one of the fruits of faith, a lack of such experience doesn't mean a person is unregenerate.