Winger, Thomas M. "Introduction: Purpose and Themes." Ephesians. St. Louis: Concordia Publishing House, 2014, 138-148.
Winger observes that among commentators, most, especially those who take Ephesians as a circular letter, also miss elements of pragmatic purposes which Winger finds clearly present (Winger 2014, 138-139). Specifically, Winger finds a strong emphasis on rejecting false teachers, though the letter does not mention any specific false teachers (Winger 2014, 139). The theme of false teaching is present in Acts 18-20. It does not seem to Winger that this was a warning about a hypothetical situation which could some day arise. It is rather a present threat. Winger identifies the teaching as a syncretistic faith in which Judaism and Gnosticism were combined with Christianity (Winger 2014, 140). The faith in Jesus was easily replaced by a faith in knowledge.
Winger sees the distinction between "us" and "you" in Ephesians as quite important (Winger 2014, 141). While this may simply signify a difference between newer and older converts, Winger takes the intended contrast to be that of Jewish Chrsitians and Gentile Christians. This distinction is made relatively clear in Ephesians 2:11-12, where "you" refers to gentiles (Winger 2014, 142). The strong warning is to not return to a futile life, but to remain in Christ.
Baptism, in Ephesians, serves as the theme which unifies all the works of God in His church (Winger 2014, 144). Winger sees this as a sacrament which is intended to create unity. Winger sees baptism as the premise on which all the work of Christ in believers is done, described in Ephesians 1:13-14 (Winger 2014, 145). Winger notes that authors in antiquity were typically willing to admit baptism as a central theme, while modern commentators are less so (Winger 2014, 145).
Winger notes briefly that ecclesiology, christology, love and marriage provide us with categories for most of the distinctives of Ephesians aside from the Jew/Gentile relationships and the baptismal life (Winger 2014, 147). The letter describes all our baptismal relationships happening in the context of the Church.