I heavily agree that Big Mom isn't using her fruit to its full potential, but not because of having many Homies. My problem is that she uses them in boring, very limited ways dictated by raw strength such as holding the Homies in her hands. In contrast, Enel and Ace used their corresponding Logias in extremely memorable ways. Ace created fire bullets and bombs, lances, pillars, and gigantic fireballs. Enel created even bigger attacks than Ace, superheated the environment, restarted his heart, and shaped his electricity into creatures. The only thing Big Mom's elements has over them is the ability to create thunderstorms without the Ark Maxim, and maybe superior size to Entei.
I think Napoleon is a pretty good Homie and better than a normal sword. It's easier to carry than a normal sword and can transform into any type of sword. However it has the same problem as Zeus and Prometheus: a lack of creativity or synergy. Napoleon has no flying slashes, swordsmanship technique, Armament Haki attacks, or slashes that incorporate the elements.
Big Mom's abilities should've demonstrated versatility, adaptability, and mastery over all her skills.