y'know... thinking on it... Yun's fighting style, besides the Spy, also seems to fit the fighting style of an Alchemist. The only thing needed I think is catalyst potions (catalist potions are like liquid spells in vials. You either throw the vial or splash a target with the potion and the potion catalyzes with the air or the magic in the air to become the effect.
Some examples would be a Fire Catalyst would be a potion version of Napalm, where it would either become a wave of fire by catching fire once free of the vial, or catch whatever it was splashed over on fire. A Water Catalyst would turn into more water by volume than the ammount of potion (would not be good for supplies, pretty sure all of the excess water would be temporary). An Earth potion would either expand and harden as it spread out or became a Splash Potion of Petrification or something along those lines.
Another use would be as building blocks for other elemental spells, allowing the user to cast spells too high leveled or too high a mana cost for them normally.