Your question ends asking this:
"In other terms, is there a way to conceive Christianity refusing the concept that Jesus was the son of God?"
It would be a clear "NO".
To say that Jesus is just like any other great Godly man having special friendship with God, as you have put it in one of your comment, is to look at those places in Bible where Jesus is equalled with God, as major flaws and contradictions in the Bible. To take Jesus in this manner and to say that He was only human and with no divine nature is to reduce the whole Bible into a bundle of inconsistencies. All those verses in Bible where Jesus is sometime portrayed as human and sometime as Divine, remains in harmony with each other especially in New Testament, only when we accept Jesus as having both human as well as Divine nature. Without this we would be representing Christianity in complete contradiction to the Old Testament as well as what we have in New Testament.
We cannot overlook all those verses where Jesus is clearly portrayed as having Divine nature. He was crucified for saying that He was Son of God. Further in John 8:58 He declares:
John 8:58 Jesus said to them, “I tell you the solemn truth, before Abraham came into existence, I am!”
Then we have at other places where Jesus forgave third person’s sins. If you do something against me, I have the right to forgive you. However, if you do something against me and somebody else comes along and says, "I forgive you," what kind of cheek is that? The only person who can say that sort of thing is God himself, because sin, even if it is against other people, is first and foremost a defiance of God and his laws. So along comes Jesus and he says to sinners, "I forgive you." The Jews immediately recognize the blasphemy of this. They react by saying, "Who can forgive sins but God alone?" Not only did Jesus forgive sin, but he asserted that he himself was without sin. And certainly sinless-ness is an attribute of deity. as if it is against Him, equalling Himself as God and many places He equalled Himself with God. All these events and quotations would glaringly be biggest contradiction which would stare at Christianity and for which there would be no plausible explanation to offer.
In the verse below, we find Jesus giving the highest honour to John the Baptist and that John is more than a prophet.
Matt. 11:9-11 What did you go out to see? A prophet? Yes, I tell you, and more than a prophet. This is the one about whom it is written: ‘Look, I am sending my messenger ahead of you, who will prepare your way before you.’ “I tell you the truth, among those born of women, no one has arisen greater than John the Baptist. Yet the one who is least in the kingdom of heaven is greater than he is.
This would mean that Jesus makes Himself smaller than John, which cannot be. Since John was someone who was more than a prophet, it only shows that Jesus was not just a prophet or someone more than that but someone much greater than that.
Again we find in Gospel of Mathew;
Matt. 16:13-17 When Jesus came to the area of Caesarea Philippi, he asked his disciples, “Who do people say that the Son of Man is?” They answered, “Some say John the Baptist, others Elijah, and others Jeremiah or one of the prophets.” He said to them, “But who do you say that I am?” Simon Peter answered, “You are the Christ, the Son of the living God.” And Jesus answered him, “You are blessed, Simon son of Jonah, because flesh and blood did not reveal this to you, but my Father in heaven!
And finally: Early in the Old Testament God introduced this idea of one innocent being shedding its blood in place of the sinner’s. However the solution of sacrificing bulls and goats and lambs for the sins of each person’s sin was a temporary fix. The next year, another animal would have to be sacrificed for the same person. A more permanent solution was needed, as noted in Hebrews 10:4:
For it is impossible for the blood of bulls and goats to take away sins.
That meant a human was needed to die for humans’ sin. But all humans are sinful, so another sin-filled person dying for us just wouldn’t work. A human without sin was needed.
But ever since Adam, every human born is sin-filled, so how could a sinless man happen? The only way was if God did it Himself.