First off, I'd like to apologize in advance for this being only slightly related to FFC.
So I've been playing Final Fantasy I on its GBA version again, and it's been making me reconsider the series in general. Particularly, it made me think about FF6's GBA iteration and the 'dungeon filled with dragons' that serves as bonus content. Now try to stick with the insanity that is my brain connections, because that led me to consider the revamped Earth Dragon in said dungeon who casts 'Megaton' and then 'Quake' whenever a character has the 'float' status to avoid his damage. The first spell cancels Float, and the second, well, it ruins your party.
Anyway, Final Fantasy has long held a tradition that flying characters are immune to earth-based elemental attacks, and yet there has never been ample exploration of their vulnerability to air-based attacks. Since, in the FF system, Earth and Aero are opposite elements (as Fire and Ice are and Bolt and Water are), it seems reasonable that they should have opposite effects.
So I came up with this:
There are two incompatible status bumps, called Float (the one we know) and Anchor (which is new). When boosted with one and subjected to the other, they cancel each other out. But here's the interesting part:
A character that is under the effects of Float takes no damage from Earth attacks, but double damage from Air attacks.
Conversely, a character under the effects of Anchor takes no damage from Air attacks, but double damage from Earth attacks.
This also gives the player reason to cast one or other other on an enemy, to make a follow-up attack more devastating. Hey, even certain enemies might cast one or the other on the party for the exact same reason.
If I were to build my own FF game, I'd definitely incorporate something like this.
Anyway, that's my insanity for the day.