(There's also Snack in the anime)
They are in the arc since almost 100 chapters yet outside Perospero they still have to do anything
They could be used to give fights to straw hats that didn't get a real victory in a fight in this arc yet (like weaklings and Brook) and give Law and Kidd crew something too (Bepo, Sachi, Penguin Heat, Wire....) since even a few non-veteran BMP ministers are more developped and have more interesting abilities than the average headliner. Kinda seems late for that though.
Or Oda brought them just to get beaten by the marine/blackbeard pirates off-screen at the end of Wano but IMO that would be a waste.