but i do have a leetle teeny tiny conspiracy theory of my own.
Arya.
She is in the house of the faceless men. well as a junior apprentice surely that would make her a "little brother"
She has plenty of reason to hate cersei, she is on her prayer list after all.
and i can't imagine why she would be left to just join the order of the faceless man and be forgotten about. She is the daughter of Ned Stark. she can't just becomea member of a religious order.
So i think that the Kind old man is training her for a specific mission....of which i think it is to kill cersei.