I would say that temporary race potions would be cool! Each race has its own look, feel and animation. IMO, what they could do is allow you to use a potion that gives you, say, 5 minutes, and only works while you are outside of an instance or solo duty (entering an instance would immediately remove the buff), and it would also be removed upon going into a cutscene.

Otherwise, you could fight enemies with it (which is 90% of the reason behind my suggestion) so that you can SEE what your character looks like, and your character's animations in actual combat.

This would help SE sell more Fantasias as people would indeed be able to "Preview" what their character would look like as far as animations go. I've been pondering a chance from Miqo'te to Au Ra, but I don't know... I haven't seen enough emotes, battle animations, etc to really know what my character would feel like and I doubt watching a video would really give me what I'm really looking for either. I don't want to do the Fantasia, then find out I don't like it and end up needing a 2nd to change back.