The idea is interesting however there is the problem that if Selene is the offensive one Eos will fade out of existence, we would be in the same scenario of Sb where one fairy was generally better than the other but even more ciritcal as now more dps is tied to that, imo this is what they should do

-For Aetherpact: For idk 10 fairy gauge, select a party member and the sch instantly gains 10 stacks of "insert name of the buff", effect ends upon reuse, each embrace would consume 1 of those stacks, said buff would do the following:
1st: The fairy will only heal that selected party member
2nd: Fairy spells gain 50% potency (would be weaker than today's but would be compensated with being able to cast fairy skills during its duration + lesser cost), since embrace/seraphic veil would be the only spells it only affect those
3rd: If the effect end and remaining stacks are left the recast time is reduced by 10% of the max recast time (12s if the cd is 120 for example) for each cast (so basically Aetherpact's version of quickened aetherflow)
That way you would have a fairy skill that doesnt lock you out of anything, can be used under seraph and is completely impossible to ghost, if you ghost it you'd end its effect with 10 stacks which would make it ready to be used again.

Imo the idea of Selene being the mitigation/defensive fairy and Eos being the regen/heal up fairy would fit much more, just give the dps actions to sch