I think these verses could also be considered as substantiation that the true spiritual Church has become the Israel of God:
[1Pe 2:9-10 KJV]
9 But ye [are] a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should shew forth the praises of him who hath called you out of darkness into his marvellous light:
10 Which in time past [were] not a people, but [are] now the people of God: which had not obtained mercy, but now have obtained mercy.
Exactly. The holy nation of Israel is the grafted Israel of God, not any sinful nation of people, including that of natural Israel.
And Paul in Rom 2 even includes Jews in his boldness, that the NT Christians with inward circumcision of Christ, are the only Jews
acknowledged in Scripture of God.
Rom 2:28
For he is not a Jew, which is one outwardly; neither is that circumcision, which is outward in the flesh: But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.
And I'll add even further, that the use of the word 'Gentiles' for nations in the NT, is now a doctrinal error. Unlike in the OT,
Ethnos in the NT is now properly all
nations on earth, which includes the natural nation of Israeli, Britain, American, S. African, etc...None of those nations on earth are themselves the holy nation and Israel of God. The redeemed of Christ Jesus, as you consistently quote, are from among all the nations of earth, whether Israeli, Britain, American, S. African, etc...
The natural Israelites and Jews having the God of Israel crucified, as you show, divorce themselves from the covenant promise of the Spirit, and make themselves uncircumcised to God. All nations of the earth and people, not born of Christ, are now
Gentile to God,. Whether Israeli, Britain, American, S. African, etc...
Rom 11:25
For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the nations be come in.
Members of all nations are now coming into the Israel of God on earth, until the risen God of Israel returns, and gathers the fulness of His holy nation and body to Himself in the air, fully numbered by 144,000.
Rom 11:26
And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob: For this is my covenant unto them, when I shall take away their sins.
That is when all the Israel of God, from among all the nations of the earth, shall be saved by the second coming of the Deliverer of Sion. The prophecy is not that all natural Israelites will be saved at His return, and especially not that national Israelites will be the only nation with Christians resurrected and recieved to Christ...
So long as anyone continues to reject the NT truth of two Israels now on earth, then they will remain blind to the Spirit's truth for all that repent on earth:
Rom 11:17
And if some of the branches be broken off, and thou, being a wild olive tree, wert graffed in among them, and with them partakest of the root and fatness of the olive tree;
Rom 11:23
And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again.
They will continue to preach a prophecy of division in the body of Christ between natural Jews and natural Greeks, Scythians, Russians, Brits...
It is not possible by the NT gospel and doctrine of Christ, for the seal of the living God to be upon the foreheads of only upon Jewish servants of the crucified and risen Lamb of God, to
the exclusion of lesser 'gentiles'. That was so in the beginning of Jesus' church on earth, it remains so today in the NT Israel of God on earth, and shall surely be so until His return to earth.
Unless of course the gospel is changed to another gospel, that is after the flesh, and not only the Spirit:
Gal 1:6
I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel. Which is not another; but there be some that trouble you, and would pervert the gospel of Christ. But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.