FF6 was pretty awesome yeah, and has the benefit of having been in both nations. I think Cecil would have fit into Smash more readily than Terra or Locke, though, and I'd rather have "yet another switch character" than "yet another big sword character".
If they HAD to go the sword route...they should have used Celes. She was always a favorite of mine. That opera scene remains one of my favorite moments in gaming history.