Been awhile since I played UNIEL, and I never used her, but I hear rumblings that Orie might not be in because Weiss seems pretty similar to her in terms of gameplay?
Nah, Orie and Weiss can be entirely different in terms of gameplay. Orie has her own "persona" thing, that can attack with it's sword or create a damaging force field. She also fights with kicks. Weiss can make those magical platforms and uses element spells. The only thing they both share is their type of weapon.
That would be the same as saying that Yuzuriha can't be in because of Jin Kisaragi.
Well, at least I hope so, since I want to play Orie/Weiss in this game.