In an effort to figure out how to uphold God’s covenant with the Jews, Paul must carefully forfeit all notions of Jewish law — which is what makes a Jew a Jew — while at the same time affirming the law so that Jesus is universal and that God is consistent in having a “people” at all. He does this by claiming that everyone sins and the law only demonstrates this, not that it ever was a means of righteousness.
Paul’s comments on justification are largely judicial rather than sacrificial or substitutionary. As the story of Lot goes, God is satisfied to withhold judgement against all were there but one righteous man among men. In the same way, Christ isn’t satisfaction against God’s wrath but in the demonstration that wrath isn’t necessary for the salvation of humanity. Jesus is cause for the mercy of God. Justice is served in the ultimate demonstration of the fullness of humanity as seen in Christ, significant to God, and as Logos, the fullness of divinity as seen in Christ, significant to human kind. And while there are many vagueries in Paul’s theology, it is clear that neither the life nor death of Christ change God’s mind about mankind; God, for Paul, has always only ever loved man. In this, we find Paul’s greatest challenge in presenting a very different view of God than is found in the Old Testament. What’s nearly as clear is that Paul never intends to suggest salvation is God changing his mind about you because of Christ.
Paul never fully develops a theory of atonement, but I would suggest that he supposes Jesus undoes what began in Adam, just as universally, and belief in Jesus isn’t efficacious for salvation but is illuminating to the way we are intended to be as human beings in the world. This is why he states “for everyone, once and for all but especially those who believe”; 1 Timothy 4:10, Galatians, and so on, and in as much as these are debatably Pauline.
It seems that if the Jew is required to accept the Gentile through Christ as presented by Paul, then because of Paul’s theology, the Christian must also accept the full universalism of the salvation of humanity through Christ irrespective of our beliefs about Christ and only better understood in reflecting on the humanity and divinity Christ represents.
Just a thought.