Well, as a suggestion, you could remove the angelic spells from LA Marignon (after all, they don't rely on angelic support anymore; quite the opposite, in fact), and add them to EA Ermor. Obviously, Reascendance would still be used for LA Marignon.
This would also open up the possibility for MA Ermor 'Fallen Angel' Summons (I guess something like Morrigans?), and quite possibly Ashen Empire skeletal angels (physically resembling the Prince of Death, perhaps?).
Getting back to the Ophanim, I guess it's mainly a question of what it takes to summon them, and what they do. They appear to be thugs of some sort, and (at a guess) they're summoned with Fire and Air. Given that Pythium doesn't get Fire magic easily, access might not be the balance concern it could otherwise be.
You know best, of course.
