Hi Dovekin and Bonaventurian, they are known as choirs according to St. Thomas Aquinas in Summa Theologiae, in the first choir you have seraphims, cherubims, and thrones also known as ophanims in the Book of Enoch.
The seraphim in Isaiah have six wings and the cherubim in Ezekiel have four wings, four faces - man, lion, ox, and eagle, with eyes all over their bodies. Now what’s interesting about the Four Living Creatures is they have six wings like the Seraphs and each of them has eyes all over their bodies like the cherubs; and one face each - man, lion, ox, and eagle, instead of four faces each. Which made me wonder if they are a choir of their own above the seraphim, cherubhim, and ophanim. Hence, Ten Choirs of Angels instead.
I like your theory of the Four Living Creatures or Evangelion possibly being the Four Evangelists: Matthew, Mark, Luke, and John. With John portraying them as angels symbolically and figuratively. I agree with your theory of Mother Mary having a position higher than the angels of Heaven, since she is the Mother of God and Queen of Heaven, a title and role given to her by God. I also agree with your theory of St. Michael the archangel, even though archangels are part of the third choir which is lower than the first choir, it was Michael along with God’s Powers who defeated Lucifer, the Pricipalities and Powers in the War of Heaven and to this day they still fight each other in the unseen world for our souls. Michael is even considered the Prince of the Heavenly Host, and he is one of the seven archangels that stands before the Throne of God and knows what He looks like along with the other six archangels.