I've downloaded the game and your idea is absolutely amazing. I'd never had though of it.
I've actually done mine with faces showing different status (normal, critical, taking damage, attacking)
and done a script to alter them in battle.
If anyone is interested in that, tall me and I could easily come up with a tutorial or something like that.
Although your method requires some work, it's much more smother and gives another atmosphere to battle. Good job.