The gymnastics the English dub of Houseki no Kuni puts itself through to never use any third person pronouns for the gems needs to be heard to be believed.
While I was half asleep, I came up with this idea after having been at a sportsfest celebration. I thought: "Hey it would be funny if the gems played badminton or something"
So I drew this all in like 20 minutes in hopes I remembered the concepts I somehow made half asleep. Basically, Kongo assigns Phos to make events and recreational activities for the Gems to enjoy. Phos, pretty much out of ideas, goes to Dia like in the original story, and gets inspiration from her technique of deflecting the Lunarian's arrows.
So Phos decides to enlist Dia's help in making a game that is pretty much Badminton (But with a baseball bat i guess).
In this AU, Phos also makes a promise to Cinnabar, though a bit different. Phos promises Cinnabar to give them a way to bond with the other gems without their poison getting in the way. So now we have the wonderful idea of Cinnabar playing badminton because of Phos encouraging them.
I have other ideas like Phos somehow inventing Ice Hockey with Antarc in the winter arc. And Phos and Alexandrite making board games. But those will be spoken of on another day.
I have watched the HNK anime a year ago and made this with my very bad memory of the plot, so i'm not sure if any of this will make sense, but I hope this AU is at least pretty decent enough to exist.