If you want a deeper description of all the macro-able commands already available in beta, please consult this thread
To change classes with a macro, first we need to change the weapons in order to pass the verification for the abilities. Hint: The game still have serious issues to recognize ability names and equipment to by pass this problems I recommend you to copy the exact capitalization and put all the names between quotation marks ["]
Then we can equip every action available for our level, the basic action for our class (i.e. Gladiator "Light Slash") will be equipped by default so we can just start from the slot 2 directly.
This would be a sample for a level 8 Gladiator switch (with the basic gear)
/equip main "Weathered Gladius"
/equip sub "Worm-eaten Square Shield"
/equipaction 2 "Guard"
/equipaction 3 "Phalanx"
/equipaction 4 "Rampart"
/equipaction 5 "Circle Slash"
/equipaction 6 "Red Lotus "