Oda has created a unique opportunity to make Brook the star of this arc in fighting back against Imunko. Something more than him shouting Gunko’s name and a sad flashback that makes Imu lose control over Gunko. It would be cool if Brook was allowed by Oda to fight Imunko and the demons in par with the monster trio.

Sadly I doubt Oda or his Editors would ever risk a side strawhat outshining their golden gooses.