Smoothie is a swordsman, a female swordsman just like Kuina.
Also I don't think Zoro should learn fire cutting. Fire is such an overused power in One piece, it would just be better if he learned his own abilities or created a new form of asura. Each of the m3 have their own elements, Sanji is fire, Jinbei is water, Zoro should be air(air slashes) or possibly lightning.
anyways, King should be able to fly in hybrid form at least.