These are the Possible Letters that have yet been used in the naming process of Warframes
My idea simply being that maybe in the future, we at least have 1 warframe to each letter
Iam not sure about how X or Q would make it in though.
X would probably be another Asian inspired warframe, Xun-Jon, perhaps?
Xao-Ba, Xefos, =o
Q could be like Qlilbon, -[KLILL-BOHN}, Quarva, Quentos, Quayfa, Qinito
Its just a