I think I see your point. If I do, here's where you're in error.
Saul was a Jew, a Hebrew of Hebrews, a member of Israel. God owned them ALL from Moses onward and was entitled to "draft" whoever among them He chose for His purposes. So He did with Saul/Paul.
We, however, are born aliens from all the covenants and promises, saved and saveable only by grace. NO ONE...neither Jew nor Gentile...comes to God today except via the Gospel of the grace of God.
GT (and most of TOL, and most of Christendom) rejects that saving Gospel in favor of various works/abiding/perseverence gospels that only appeal to proud religious flesh but cannot forgive nor justify them.
There is no potential in any such because they're dead in sin. And when any of us is saved, the old man is STILL counted by God as dead so that all he/she now has, and is, is of Christ.
For that reason I disagree with your analysis of GT's, or anyone's, potential.