After finishing a book on Paul and arguing at length that Romans is concerned both with ethnocentrism and a quasi-legalism (what I call "ethnocentric nomism") I discovered that Augustine himself said something similar long ago:
The Letter of Paul to the Romans, in so far as one can understand its literal content, poses a question like this: whether the Gospel of our Lord Jesus Christ came to Jews alone because of their merits through the works of the law, or whether the justification of faith that is in Christ Jesus came to all nations, without any preceding merits for works. In this last instance, people would believe not because they were just, but justified through belief; they would then begin to live justly. This then is what the apostle intended to teach: that the grace of the Gospel of Lord Jesus Christ came to all people. He thereby shows why one calls this “grace,” for it was given freely, and not as a repayment of a debt of righteousness.Paula Fredriksen Landes, Unfinished Commentary on the Epistle to the Romans I.1, Text and Translations 23, Early Christian Literature, series 6, ed. Robert L. Wilken and William R. Schoedel (Chico, CA: Scholars, 1982), 53.
Why Reformed and NPP commentators have missed this passage remains oblivious to me. Of course, I count myself among the ignorant!