Kajiura keeps reminding us that FictionJunction = Yuki Kajiura, and her alone. Everyone else is a feature for as long as their paths align.
Iunno what the reasons for Emiko's split with her management are (do we ever really know?) but maybe we live in a time/economy when artists/talent don't want to pay commissions/can't afford to support a management company (or vice versa). Obviously ignoring a situation where they just don't have a good working or personal relationship.