Two things: this is an interesting theory. I myself had placed the Jotun as the defenders at the Gate and the Aesir as the protectors from the defenders. That is to say, that Odin was replaced by TITANIA, not Mab. My thinking was that the Aesir cut a deal with the Tuatha de Denaan and the triune goddess. With faith in these pagans waning, there was an imbalance between Aesir and Jotun. By combining the Fae with the mother goddess, there was enough power to defeat the Jotun, but the power gained by the Gate responsibilities forced the triune goddess to split into two. That, plus pinning their power to a cyclical, scientific phenomenon, created a pretty solid balance.
So I think there was no Winter Court before they became the defenders. Just Mother (Unknown, but dead now), Maiden (Mab), and Crone (Mother Winter).
Second, some posters are misinterpreting the Hades/Satan thing. Hades is the ruler of his domain. The CEO. Satan is an Officer. He has a board he needs to answer to (... Legion?). that's the difference.