>...the others are mixed into various non-Jewish nations of the world
Yes, mostly CELTIC nations, which are Israelite, but not Jewish.
>and are not aware of their part-Judaic[ED: ???] or Abrahamic descent.
That is changing.
>To claim an inheritance from deceased A, descendant B would first HAVE TO KNOW he WAS so descended, and that test is flunked.
Now that's just plain silly. When a Will shows up long after the deceased has departed, if that Will clearly spells out the inheritors, it's just a matter of finding them. While this has taken a while, God has no statute of Limitations. The NorthernKingdomIsraelites/Lost Tribes of Israel/Celts/Americans&Europeans have been found. And their claim has been filed.
>I know what you mean of course, that when Elijah comes he will make these genealogies plain,
and many non-Jews and anti-Semites will learn of significant Jewish bloodlines
This is not about "Jewish bloodlines". Its about ISRAELITE blood lines. And you well know that some Jews are Israelites, but the vast majority of Israelites are not Jews.
>I do not know, but it is very, very, likely that the great majority of these have already historically been Christian and thus saved under another method.
Agreed. Which leads off to another topic, that is, can any Jews be saved under the legalism of Judasim?