Thank you for documenting your challenged playthrough on the forums, LunarWeaver.

I have played a similar playthrough of Final Fantasy X-2. Yuna was automatically equipped with an accessory to give her access to White Magic from the start of the game, and Rikku was equipped with an accessory to give her access to Black Magic at the start of the game. Paine was equipped to have better statistics than the other two characters. My reasoning for allowing Yuna and Rikku to use White and Black Magic was because of events in Final Fantasy X.