Bottom line is, you have your position and I have mine. I haven't been given any clear,solid scriptures buttressing your position.
The Patriarchs/Prophets are silent on it. The biology wouldn't even permit it. Man was created a little lower than the angels (psalm 8:5). Have you ever seen offspring resulting of bestiality? Man and the lower life forms, without gene technology? But as it is claimed, these fallen angels got married (the word wife is used) and had offspring. I will stand by the aforementioned psalm.
They (Noah) may not have been born of the 'serpent seed', but they may as well have been.
If they may as well have been, isn't Christ's bloodline already compromised then?
Luke 3:35-38
the son of Simeon, the son of Judah, the son of Joseph, the son of Jonan, the son of Eliakim, the son of Melea, the son of Menan, the son of Mattathah, the son of Nathan, the son of David, the son of Jesse, the son of Obed, the son of Boaz, the son of Salmon, the son of Nahshon, the son of Amminadab, the son of Ram,
the son of Hezron, the son of Perez,
the son of Judah, the son of Jacob,
the son of Isaac, the son of Abraham,
the son of Terah, the son of Nahor,the son of Serug, the son of Reu,
the son of Peleg, the son of Eber, the son of Shelah, the son of Cainan,
the son of Arphaxad, the son of Shem,
the son of
Noah, the son of Lamech,
the son of Methuselah, the son of Enoch, the son of Jared, the son of Mahalalel, the son of Cainan, the son of Enosh, the son of Seth, the son of Adam, the son of God."
There you have it. Joseph and Mary were direct descendants of David, as the prophecy said. So if Noah was compromised in the tiniest bit, so was Christ. But since i believe the nephilim were ordinary human beings, there's nothing for me to stretch.