There are only 4 main characters in this manga, that includes Kakashi, Sasuke, Naruto, and Sakura. Hinata is a supporting character. However, if you meant that she has the second most amount of relevance, Tsunade, Ino, Konan, and Kushina say hi.
You compared Kaguya and Hinata because they are both female, that's the only concrete evidence you have. Kaguya didn't have byakugan, even though the Hyuuga's eyes are pale, you can still see their iris. With Kaguya, you cannot in fact it looked like her eyes were entirely white or she had none (obviously she had eyes, but she looked somewhat soul-less.) So no byakugan. Then you stated the fear factor, but no one fears Hinata. So that doesn't count either. It's possible because you cannot rule out anything w/ Kishimoto (never expected wired susanno or Might Dai), but I'm sorry I just don't see it.