Heck, I just have this picture of Cloud and/or Leon trying to do the whole "stoic emo hero" thing near Tohru (or, gods help them, a Tohru with an infusion of Aerith backbone) and finding themselves sat down, fed their favourite meal, and relentlessly Cheered Up. By about five minutes into things they'd be willing to agree to rooming with Sephiroth, Hades, Ansem and Xemnas, if only to get her to *SHUT UP* for long enough for either of them to get a word in edgeways.
I still want to let her loose on Organisation XIII. I suspect Axel and Demyx might be the only ones even vaguely able to cope with her. Besides, her canon ability to make anybody feel like Somebody Special would be interesting to observe on the Nobodies. Between that and her unique way of looking at the world (honestly, she makes Pollyanna look like a chronically depressed cynic at times) I figure she'd be able to wreak havoc on The World That Never Was armed only with a picnic basket and a thermos of hot chocolate.