I applaud your interesting approach to the idea of "we are all Jews" in spirit, but I think it flies in the face of Paul himself who said there was no Jew or Gentile (Greek) in Christ. I suspect you mean we are "all the same" in Christ.
What I tend to see is that one who promotes the Law invests their identity in Judaism and that leads to essentially thinking in part that one is "like a Jew" or to some point a Jew in itself. This connection also flies in the face of Paul who essentially says.... there is no "identity" as a Jew in Christ.
        
        
     
The NEW Covenant is made with "The House of ISRAEL" in Heb 8 and Jer 31
AND this is the reason why - 
And as the context for that - Romans 9 "
they are NOT all Israel who are children of the flesh".
Rom 9
6 But it is not that the word of God has taken no effect. For they 
are not all Israel who 
are of Israel, 7 nor 
are they all children because they are the seed of Abraham; but, “In Isaac your seed shall be called.”  8 That is, those who 
are the children of the flesh, these 
are not the children of God; but 
the children of the promise are counted as the seed
Rom 2
25 For circumcision is indeed profitable if you keep the law; but if you are a breaker of the law, your circumcision has become uncircumcision. 26 Therefore, if an uncircumcised man keeps the righteous requirements of the law, will not his uncircumcision be 
counted as circumcision? 27 And will not the physically uncircumcised, if he fulfills the law, judge you who, 
even with 
your written 
code and circumcision, 
are a transgressor of the law? 28
 For he is not a Jew who is one outwardly, nor 
is circumcision that which 
is outward in the flesh; 29 but 
he is a Jew who is one inwardly; and 
circumcision is that of the heart, in the Spirit, not in the letter; whose praise 
is not from men but from God.
Rom 11
19 You will say then, “Branches were broken off so that I might be grafted in.” 20 Quite right, 
they were broken off for their unbelief, but 
you stand by your faith. Do not be conceited, but 
fear; 21 for if God did not spare the natural branches, He will not spare you, either. 22 Behold then the kindness and severity of God; to those who fell, severity, but to you, God’s kindness, if you continue in His kindness; 
otherwise you also will be cut off. 23 And 
they also, if they do not continue in their unbelief, will be grafted in, for God is able to graft them in again. 24 For if you were cut off from what is by nature a wild olive tree, 
and were grafted contrary to nature into a cultivated olive tree, how much more will these who are the 
natural branches be grafted into their own olive tree?
NIV-
25 I do not want you to be ignorant of this mystery, brothers and sisters, so that you may not be conceited: Israel has experienced a hardening in part
 until the full number of the Gentiles has come in, 26
 and in this way all Israel will be saved
 
Paul said  -- "And in this way" all Israel will be saved. Rom 11 - and what was that "way" that is described in Romans 11? answer -- it is the way of the Gospel - the Gospel where both Jews and Gentiles are saved -