Another point to consider about the 12 tribes of Israel that the society says are symbolic as 11 of those tribes are no more, surely God himself knows the lineage of each and every person who ever lived.
Just because we dont know who or where the literal decendants of the promise to Abraham are, doesnt mean Jehovah doesnt know. And therefore the Great crowd could therefore be members of the "annointed" from amongst the Gentiles, an immeasurable amount.