Jason O’Mara explained on a Marvel podcast that Mace will have to deal with a conflict of interest between the government’s stance on Inhumans and his own feelings as an individual with Inhuman powers.
As a director who genuinely wants what is best for the agency as well as the public at large, he may have trouble reconciling his personal feelings with what he needs to do in order to keep S.H.I.E.L.D. running in the post-Sokovia Accords bureaucracy.
Interestingly, Jeff Mace’s superpowers may not be as significant in battle as they are in the bureaucracy of Agents of S.H.I.E.L.D. The characters are all trying to move forward in their jobs in the wake of the Sokovia Accords that split the Avengers in Captain America: Civil War.