Though hammers were also used to deal actual physical damage in older FF games, granted not a ton, but it was still much more than WHM in XIV would ever be able to deal. So saying that, a hammer for WHM in this game would probably be purely cosmetic, it would be a weapon type better going to a DPS or tank so it gets more usage.

I would however be open to WHM having a long range type staff/rod that throws elemental blasts or a wind-based racket as seen in IX.