I like it OP, and I can't think of any devastating counterexamples off hand, but the fact that Pinkie Pie is definitely much more emotional (Slendermane) and Dash more physical -- as can be seen by her frequent associations with AJ -- might upset your theory a bit.
But in regards to this kind of thinking in general. I think it's definitely NOT reading too much into it to infer these kinds of categories, since FiM is fundamentally a show about ethics as most shows intended for younger children are. Furthermore, it's a particular brand of ethics: one associated with virtue and harmony.
This might seem like a truism, but what if MLP didn't highlight virtues but instead something else like, I dunno, utilitarianism. Would every episode then be a kind of economics lesson? Think about how different that would be? Supposedly in a different kind of society, that is how MLP would be like... ... thank Celestia?
In short, I think there is definitely something uniquely Aristotelian about MLP that you have latched onto.