I would just like to see some more canonical FF series enemy spells to be honest. I think BLU's functionality is at its peak, and gaining too much more in firepower is sure to lead us to lose firepower in other places.

Just being able to see classic spells like Mighty Guard, Beta, Trine, Laser Eye, Shadow Flare, Aqualung, Pulsar, or even *gasp* Roulette would be awesome to see make an appearance.