As a Matter of Fact.

[Pancho Frijoles]

Only a mixed heritage Hebrew would know about Jewish traditions and the Law of Moses. The "faith" the centurion expressed was in his knowledge of the Hebrew Scripture and their many references given that identify Israel's Messiah and Kinsman-Redeemer. That's all that was about. Nothing more.

That's mere speculation, and a very weak one.

First, any careful observer living in Israel could know about Jewish traditions and the Law of Moses, regardless of his genetic background.
If you lived in India por few years, you would know about Hindi traditions and laws.

Second, and more importantly, Jesus does not do any effort to point out to the supposed hybrid genetic linage of the centurion.
It is important for you. Not for Jesus.
Jesus emphasized his faith and his status as non-member of the House of Israel.

The whole thing had to do with presumed ethnicity and Peter as a hard-core believer in the accepted social norms of maintaining ethnic purity was, like James and John and the rest of Israel, prejudicial towards mixed heritage Hebrews. Imaging Cornelius talking about his ancestry in comparison to Peter or James. One could talk about being a son of Abraham naming tribe, family, and clan, the other couldn't. Somewhere Cornelius would have to say, "son of Simeon, Yakob, Herbert, Tony..."

God does not use the argument of a shared genetic lineage to encourage Peter to go and preach to Cornelius.
When Peter returns to Jerusalem, Peter does not use that argument either.

So, the story of a mixed Hebrew heritage for these Gentiles is all in your head. Not in Scriptures.
It is a fantasy... a fantasy that underpins an ethnically-based soteriology.

He does that in the context of their being a seed of Abraham.

I have already quoted from Galatians the evidence that for Paul, it was faith, and not genetic lineage, what made someone seed of Abraham.

For every "Jew" who believed in the words of Moses and the prophets believed and prayed for God to send a Deliverer "like unto [Moses]" and by believing the Scripture were Christian. The Hebrew nation is the only Christian nation on the planet. Not America, nor France, or Britain, or Australia.

That premise is unsupported by the New Testament, which stress that being Christian is a matter of the spirit and not of the flesh. That's exactly why circumcision, even when declared a sign of a permanent covenant for all Abraham seed, was later on considered optional and not relevant. Genes are flesh, not spirit.

That is what Scripture records

What the Scripture records does not support your speculations about a mixed Hebrew lineage as a prerequisite to receive and accept the Gospel. Your exegesis is poor. Your eisegesis is tragic.
Fortunately, God loves you anyway, and I know you are and continue to be recipient of his blessings.