Substituted huh?
Man A : Strives hard to please God and be righteous? too bad, God wants Christ's righteousness not yours
Man B: Lying thieving scum? It's your lucky day, you get to have Christ's righteousness
I honestly don't know how to respond to this. God wants us to be good but then sends his son down who is actually him in another form to take away our sins and save us with himself from his own wrath.
Well, at least you understand it, even if you do not accept it.
Actually, we believe that some Muslims will be sent to Hellfire because their bad deeds and sins outweighed their good deeds and acts of worship.
And we believe that there are none, including Man A above, whose sins do not outweigh their good deeds.
While Allah is Merciful with His Forgiveness, He is also Just in His Punishment. We believe that Prophet Muhammad (saaws) will make intercession before Allah on their behalf and they will eventually be released from Hellfire if they did not associate partners with Allah.
So, you do depend on an intercessor. One who stands between you and Allah, but you don't think of that person as a partner with God. Well, neither do I think of Christ as a partner with God for I think he is in fact THE one God Almighty, Father, Creator, Redeemer, and Sustainer of all humankind. And yes he interceedes on our behalf with himself. On the one hand Almighty Judge and on the other our Advocate before the throne of judgment. To our mind, a mere human would not be capable of making that appeal, but God himself, out of his love and mercy can appeal to himself and satisify his own demands for justice and righteousness that I and no other human being could ever offer.
I have great hope in the Mercy of Allah and I pray for His Forgiveness, but at the same time I fear His Wrath for the wrong that I have done both knowingly and unknowingly. While we don't claim to earn Paradise by our good deeds, we do believe that good deeds counteract and erase bad deeds.
And we don't believe that our deeds are placed on a scale. There is no point. Good deeds do not erase bad deeds. It is not like a math equation with a zero point sum. It is a standard of perfection, and no matter how good you are, unless one is perfect they still fall short of what God is seeking. Thus we are to be good not to earn anything, but for the sake of goodness itself.
How can a government pardon a crime if the criminal does not even recognize the government? Shirk is spiritual treason, and Allah will never forgive those who did not recognize His supreme authority by being devoted to other gods if they died in that state without having repented. If you committed all the sins in the world, Allah will come with an equal amount of mercy to forgive those sins provided you did not associate any partners with Him. Truly Allah is Ghafoorun Raheem (Forgiving and Merciful).
Amazingly, this is curiously close to the Christian understanding of grace. You are right that a government cannot pardon a crime if the criminal does not even recognize the government. Now you suggest that those who recognize Christ as God are committing spiritual treason. But just for a moment try to hear what Christians are saying. (I'm not asking you to accept it, but to hear it.)
The Christian says that one must place one's faith not in one's own merit, but in the work of God. That God and God alone is to be the central focus of one's life. That though you may have failed to live that way, if you will get your eyes off of yourself, and back on God, if you will repent of your sin and seek to submit yourself to God's authority in your life, then God can redeem you, reclaim you, and restore you to a position of fellowship with him such as you were originally created to live in. The first step in that process is God's unmerited love directed toward us, and the response that is needed is not some act on our part but a decision to trust in what God is doing --our actions must flow out of trusting God to be as good as his word.
The Christian hears that word, the promise of God's mercy, in the life, death, and resurrection of Jesus who we believe embodies God come among us. You may call that final belief shirk, but do you see how similar the rest is to what you described. And for us to turn our back and not trust in the work of Christ and try to be good in our own right, would be exactly the type of treason of not recognizing the government you describe.