I was thinking about writing a fanfic for IX eventually and I was trying do decide for some possible topics. I am looking for back stories which didn't get much attention in the game.
Ones I can think of
How Beatrix became General and lost her eye
Cid and Hilda's relationship before she left
How Zidane met Tantalus (I am still curious about this to this day. I'm not sure if he was a baby or already a teenager when he arrived on Gaia)
Madain Sari's Destruction (Involves the tribe of Summoners, exploring their background, culture, rituals, etc. Along with Garnet and Eiko's biological parents and Eiko's grandfather)
I'll post my fanfic in the Writer's section whenever I get through with it. Please give me your suggestions and any ideas you may have.