Ephesians 2:12 is not a reference to ancient Israel. The referent of you is the Ephesians, many of whom had not yet been born until after the cross. What had previously (once ... at that time) resulted in them being without Christ and excluded from the citizenship of the Israel and strangers of the covenants of the promise (the promise of the Abrahamic Covenant is received in the New Covenant through belief in Christ), all of this occurring after the cross, was that they were not yet in Christ, because they had not yet believed in Him. Once they believed in Him, then they were in Christ, and consequently they were made near by/in the Blood of the Christ, and consequently they were no longer without Christ (they were now in Christ) and no longer excluded from the citizenship of the Israel (they were now the saints fellow citizens) and no longer strangers from the covenants of the promise (they were now no longer strangers and they were now fellow partakers of the promise in Christ Jesus through the Gospel), as Paul explains in Ephesians 2:11 3:6.
This Israel from whose citizenship the Ephesians USED TO BE excluded (when they were unbelievers) is the Israel from whose citizenship Jewish unbelievers were NOW excluded in Romans 9:6-8. This is the Israel whose citizens are the saints (believers in Christ), both Gentile and Jew, and whose Cornerstone is Christ. In Romans 9:6-8, Paul identifies the citizens of this Israel as the children of the promise / the children of God, whom he had previously (4:13-16 / 8:14-18) identified as us/we, the saints, both Gentile and Jew, and whom he afterward (9:22-24) identifies as us, the vessels of mercy, both Gentile and Jew.
This is the part of the tree / Israel in Romans 11:16-24 / 11:25-27 that believes in Christ, from which the part of the tree / Israel that does not believe in Him is excluded by its unbelief toward Christ UNTIL the Gentiles who believe in Him have entered into the part of the tree / Israel that believes in Him, as Paul explains in Romans 11:16-24 / 11:25-27. These two parts of the tree / Israel in 11:16-24 / 11:25-27 are the two Israels in 9:6-8 (believing [New Covenant] Israel [the saints, both Gentile and Jew]) and 9:31-32 and 11:7-11 (unbelieving [Old Covenant] Israel [the Jews (non-saints)]).
These two Israels in Romans 9:6-8 and in Romans 9:31-32 and 11:7-11 are the two Israels in Galatians 4:21-31 (compare Hebrews 12:18-24). The citizens of the New Covenant Israel are the saints, both Gentile and Jew, who are the heirs of the promise, and whose city is heavenly Jerusalem, whereas the citizens of the Old Covenant Israel are the Jews (non-saints), who are not the heirs, and whose city is earthly Jerusalem. The New Covenant Israel in Galatians 4:21-31 is the Israel of God in Galatians 6:15-16.
This Israel from whose citizenship the Ephesians USED TO BE excluded (when they were unbelievers) is the Israel from whose citizenship Jewish unbelievers were NOW excluded in Romans 9:6-8. This is the Israel whose citizens are the saints (believers in Christ), both Gentile and Jew, and whose Cornerstone is Christ. In Romans 9:6-8, Paul identifies the citizens of this Israel as the children of the promise / the children of God, whom he had previously (4:13-16 / 8:14-18) identified as us/we, the saints, both Gentile and Jew, and whom he afterward (9:22-24) identifies as us, the vessels of mercy, both Gentile and Jew.
This is the part of the tree / Israel in Romans 11:16-24 / 11:25-27 that believes in Christ, from which the part of the tree / Israel that does not believe in Him is excluded by its unbelief toward Christ UNTIL the Gentiles who believe in Him have entered into the part of the tree / Israel that believes in Him, as Paul explains in Romans 11:16-24 / 11:25-27. These two parts of the tree / Israel in 11:16-24 / 11:25-27 are the two Israels in 9:6-8 (believing [New Covenant] Israel [the saints, both Gentile and Jew]) and 9:31-32 and 11:7-11 (unbelieving [Old Covenant] Israel [the Jews (non-saints)]).
These two Israels in Romans 9:6-8 and in Romans 9:31-32 and 11:7-11 are the two Israels in Galatians 4:21-31 (compare Hebrews 12:18-24). The citizens of the New Covenant Israel are the saints, both Gentile and Jew, who are the heirs of the promise, and whose city is heavenly Jerusalem, whereas the citizens of the Old Covenant Israel are the Jews (non-saints), who are not the heirs, and whose city is earthly Jerusalem. The New Covenant Israel in Galatians 4:21-31 is the Israel of God in Galatians 6:15-16.