I agree. It's all scriptural.
"As for Me, behold! My covenant is with you, and you shall be a father of many nations [more literally translated from the Hebrew as: a multitude of goy]." Genesis 17:4
"I know, my son, I know. He (Manasseh) also shall become a people, and he also shall be great, but truly his younger brother (Ephraim) shall be greater than he is, and his seed shall become a multitude of nations [more literally translated from the Hebrew as: the fullness of Goy]." Genesis 48:19
"For the head of Syria is Damascus, and the head of Damascus is Rezin; and within sixty-five years Ephraim shall be broken so that it shall not be a people.
And the head of Ephraim is Samaria, and the head of Samaria is Remaliah's son. If you will not believe, surely you shall not be established." Isaiah 7:8-9.
"And He said, Call his name Not-my-people. For you are not My people, and I will not be for you.
Yet the number of the sons of Israel shall be as the sand of the sea, which cannot be measured nor numbered. And it shall be, in the place where it was said to them, You are not My people, there it shall be said to them, You are the sons of the living God.
Then the sons of Judah and the sons of Israel shall be gathered together, and shall set over themselves one head, and they shall come up out of the land. For great shall be the day of Jezreel." Hosea 1:9-11
Romans 9
22 What if God, willing to show His wrath and to make His power known, endured with much long-suffering the vessels of wrath fitted to destruction;
23 and that He might make known the riches of His glory on the vessels of mercy which He had before prepared to glory;
24 whom He also called, not only us, of Jews, but also of the nations?
25 As He also says in Hosea, "I will call those not My people, My people; and those not beloved, Beloved."
26 And it shall be, in the place where it was said to them. "You are not My people; there they shall be called sons of the living God."
30 What shall we say then? That the nations, who did not follow after righteousness have taken on righteousness, but a righteousness of faith.
31 But Israel, who followed after a law of righteousness did not arrive at a law of righteousness.
32 Why? Because it was not of faith, but as it were by the works of the Law. For they stumbled at that Stumbling-stone;
The confusion comes in for some because Paul uses the word "Jews" and "Israel" interchangeably, but it's obvious that he believed what you are saying (and what I have been saying for many years), because if he did not, then he would not have quoted Hosea 1:9-11 when including the Gentiles in the promise that the very people who God said are no longer His people / not His people would one day be called "the sons of the living God".
For the first time I realize that it sounds oddly like the claims in the book of Mormon, except that it's true, and it's also true that many Gentiles in the West after having DNA tests discover they have a small percentage of Semitic genes somewhere in their ancestry, whereas American Indians do not (as far as I know), unless they are mixed with Europeans in their ancestry, and those Europeans have Semitic genes in theirs.
But genetic ancestry never made any difference to God when He promised Abraham, "As for Me, behold! My covenant is with you, and you shall be a father of many nations [more literally translated from the Hebrew as: a multitude of goy]." Genesis 17:4.
It was God's first promise to Abraham. Abraham's seed (Jesus) through whom all the families of the earth would be blessed, would descend from Isaac, and Jacob, and Judah. His seed is not "seeds" as Paul stated, it's one seed: Christ. Salvation and God's election is only found in Him, Jesus, the seed of Abraham.