So with the whole class roleplaying the other class thing, what could the consequences of a mage of light roleplaying a thief of light

It would be that they’d act like a Thief of Light, and be a tad unhappy or not efficient. Really all there is to the Roleplaying System, is that someone goes ‘oh, this person is cool!’ and then try to act like them, which often leads going against their own strengths and being less effective, but occasionally can be compatible with their own powers.

Think of Vriska, she wears her admiration of Mindfang on her sleeve while she’s alive, and she’s always the one Making shit happen, the one being the Fairy of the group, the one trying to Improve Tavros.