[Angelus Errare]

"But God said to Abraham: 'Do not be distressed about the boy or about your slave woman. Heed the demands of Sarah, no matter what she is asking of you; for it is through Isaac that descendants shall bear your name. As for the son of the slave woman, I will make a great nation of him also, since he too is your offspring.'"

- Genesis 21:12-13

"As she sat opposite him, he began to cry. God heard the boy's cry, and God's messenger called to Hagar from heaven: 'What is the matter, Hagar? Don't be afraid; God has heard the boy's cry in this plight of his. Arise, lift up the boy and hold him by the hand; for I will make of him a great nation.'"

- Genesis 21:16-18

[Jael]

Genesis 16:11 And the angel of the LORD said unto her, Behold, thou art with child, and shalt bear a son, and shalt call his name Ishmael; because the LORD hath heard thy affliction.

12 And he will be a wild man; his hand will be against every man, and every man's hand against him; and he shall dwell in the presence of all his brethren.

[BenR2]

"But God said to Abraham: 'Do not be distressed about the boy or about your slave woman. Heed the demands of Sarah, no matter what she is asking of you; for it is through Isaac that descendants shall bear your name. As for the son of the slave woman, I will make a great nation of him also, since he too is your offspring.'"

- Genesis 21:12-13

May I suggest that the operative word in the passage that you have cited is "also."

Here the LORD graciously promises to make of Ishmael "a" great nation (which promise, incidentally, has been overwhelmingly fulfilled in the Arab peoples literally, and in all Muslims, spiritually).

Nonetheless, the verse I cited (Gen 21:12) trumps yours: Abraham's seed via Isaac is the line of promise, whence sprang the Messiah, the LORD Jesus Himself.

Stick to your day job: A bible exegete you ain't.