Hmm, perhaps if we have the classic Strength, Dexterity, and Constitution as physical stats, we can try and mirror that with magical stats? Intelligence, Wisdom, and Charisma can potentially remain as RP-only things, if necessary. 

Magic Potency: Denotes the power of a creature's magical abilities. Fireballs are bigger and burn hotter, barriers are tougher and more resilient, etc. The magical equivalent to Strength.
Magic Refinement: Denotes the precision of a creature's magical abilities. Fireballs can be shaped and can fly further, barriers can be shaped and are cheaper to maintain, etc. The magical equivalent to Dexterity
Magic Resistance: Denotes a creature's level of protection against hostile or otherwise unwanted magical effects. Allows a creature to shrug off mental attacks or better protect themselves against magical fire.

Names and effects can be changed of course, and really, I'm just spitballing.