The Ant King chapter of the full-time hunters was one of them. This chapter told the story of the ant kingdom and the conflict between the ant kingdom and humans. In this anime, we saw many classic battle scenes and unique character settings, some of which left a deep impression on us.
One idea could be a male OC who has a special ability related to ants. For example, he can communicate with them on a deeper level than the normal nen abilities in Hunter x Hunter. He could use this to his advantage in battles or to gather information. Maybe he discovers a hidden ant colony that has some unique secrets about the world of Hunter x Hunter.
The Hunter x Hunter manga is unfortunately not complete. The author has faced various issues that have led to intermittent breaks and an unresolved storyline.
The Hunter x Hunter manga has indeed concluded. However, the ending might have left some fans wanting more or with mixed feelings depending on their expectations.