A really interesting plot might be a story where Percy has to protect Artemis from a curse that is slowly draining her power. This could involve him going on a quest to find a cure, facing many challenges along the way, and developing a deeper understanding of Artemis. There could be some really cool moments where Percy uses his water - based powers in unique ways to help Artemis. Also, there could be some great character development as they interact more and more. This type of plot would also allow for exploration of the relationship between a male hero and a female goddess in the context of the Percy Jackson universe.
Perhaps a plot where Artemis is somehow transported to the modern world and Percy has to help her adapt while also hiding her from the other gods who might not take kindly to her being in the mortal realm. This could lead to some humorous situations as well as some deeper exploration of Artemis' character as she experiences things like modern technology and different social norms for the first time.