Major quality: fatigue from might


I do not recall that there is something like a major supernatural virtue or quality which allow a magical being (or other realm but RoP:M contains exhaustive rules compared to the other 3 books about creating creatures) to use is might from the might pool as fatigue.

I recall there is "fatigue mastery" which allow the opposite: using fatigue to gain 5 might point per level.

Would it be obviously unbalanced to allow the opposite?
I could see some beast with "no fatigue" using his large might pool to exert his might in physiscal combat (to use double attack ability for example).

Would you allow this major virtue or major quality?

Thanks for your answers,