Classic Final Fantasy wouldn't really benefit from the Wiimote much, if you ask me. Really, there wouldn't be a way to do it without changing the game's interface pretty significantly, but then the game would be working around the controller just for the sake of working around the controller. There's nothing about the main Final Fantasy titles as we know them that would really benefit from motion control.

However, a lot of Final Fantasy games have at least small amounts of environment interaction. It consists of walking up to something and pressing either X or A, depending on what system you're playing on. Then, something happens, and if it didn't involve pushing a button, your character will exclaim what they did. I think it would be pretty cool if you could interact with the environment a bit more directly, like some classic adventure games had you do.

Edit: Then again, the Playstation Move is a new peripheral. It would be pretty crappy if all the developers used it for were just tiny things like that, and not something that really defines the whole experience.