No, they are still around, just not as the people in charge. Besides, look at the Lords of the Nine; most of them are lifted straight from the same sources. Although frankly I don't see it any differently than using the Olympians or the Aesir or any other group of divinities, I can certainly change it to fit the theme of the project. Personally I like the idea suggested earlier of having the Seraphim be other names by which the Hebdomad are known by.

Good to see that someone likes Sandalphon though.