I remember back in Final Fantasy Tactics, when your blue mage learned a spell, you would see a "!" above his head, sort of like what we see for abyssea procs.
It'd be nice to have a piece of gear or something that would allow us to see a "!" when a spell is learned, so we don't kill the enemy before we've learned it. (If we can help it)
Maybe make it an upgrade for the Magus Torque.