I really like the idea of a weak magic but strong healer. Though Aeris is THE magic user in the current version of the game (for me, at least), so it could mess up the character balance. Having strong magic stat would be even more special. I think Vincent would have the highest magic, maybe, with Cloud, Cait, and Yuffie (?) having reasonable magic.
I'm not sure if I'd go through with this if I were Chief, but I'd definitely be interested to see how different my party would look without Aeris being such a nuclear submarine of a caster- she's been in pretty much all of my late-game fights.
Thinking about it, I've mostly used her for maximum damage with W-Magic, Quadra Magic = Ultima/Pearl/Break etc, as well as her limits (though I'm avoiding using 'peerless', or even 'fury brand', because they're so OP)
I've also used Cait Sith with the chocobracelet for getting through Nemesis in the Battle Square ("Miss!"), Cid's lucky lucky weapon and double cut for great justice, Vincent as a great secondary caster, Yuffie for SPEED, and a decent sprinkling of the other characters- nobody's been neglected too badly, I don't think.