Mikumo = Basara. She's not interested in fighting, more interested in power of music like Basara. She's also a bit stubborn like Sara Nome. Basara often disappears to find music challenges in the galaxy. He's interested in hearing others sing and challenges them. Basara is unafraid of being in the middle of combat. Just like the scene that Hayate thought Mikumo is crazy jumping in front of combat, we all know that Basara was the 1st to do that.
Freyja = Her design is sort of like Elma from Macross 7 Dynamite, she is sort of like Mylene now that she has Fold Receptors. Maybe like Ranka in some other ways.
Hayate is a bit like younger version of Isamu, hot shot but not ready for prime time yet.
Messer = Gamlin. Determined and stubborn.