Reading your talk I thought of a mod that might be worth doing in the future, imagine replacing all the silly characters that are over the top, for example Eiko and Quina with characters that are a bit more mature. Maybe the summoner in the ruined village could be garnet's older sister, or maybe an old granny. Quina could be replaced by some character that isn't so fat, maybe some muscular wild man.
The modeling and animation wouldn't be difficult to do, what might be difficult is to remake entire cutscenes, thinking specifically of the love letter event in Alexandria. Just throwing this out there, because if Final Fantasy is suffering from anything it's silly characters.
I don't think we are able to utilize custom meshes quite yet for player characters, so my current mission is to try and give some characters some alternate costumes that already exist (hooded Zidane, Knight Zidane, hooded Garnet, dress Garnet, short/long hair, etc). I could use a list as to what model is what, or something to preview the FFIX models with. The autodesk FBX previewer closes as soon as any FFIX model is opened.
I've personally always had a soft spot for Eiko and Quina, but I like the idea. The pre-rendered cutscenes would be out of the question. Scripted cutscenes would probably be more doable.