Selene doesn't have to necessarily have the same abilities as before. I was thinking one EoS could be single player heals vs Selene AoE Healz. Being able to summon both or utilize a more "summoner" style of heal pets? Maybe a one for one translation for example...
Eos = Garuda, Selene = Titan, "New Fairy" = Ifrit, Seraph Or "Titania" = Bahamut, "Feo/Titania" = Phoenix. Something like that.