Lucca from Chrono Trigger definitely planned next.
Eventually, when I'm experienced enough to pull it off and brave enough- Harley Quinn from Batman the Animated Series (I've already done Joker, so being able to do both would be hilarious
Others I'd like to try-
Bad Girl - No More Heroes
Margaret Moonlight - No More Heroes 2
Bridget - Guilty Gear
Human Fluttershy (possibly...) - My Little Pony: Friendship is Magic