A fanfic might explore a backstory where Cheadle and Pariston knew each other before they became important figures in the Hunter Association. Maybe they were trainees together and had some sort of rivalry or friendship that has been long forgotten but resurfaces during a crucial event in the story. It could show how their past relationship affects their present actions and decisions.
You can start by looking on fanfic websites like Archive of Our Own (AO3). It has a large collection of Hunter x Hunter fanfics and you can search specifically for ones that involve Cheadle and Pariston. Just type in their names in the search bar and you'll get a list of relevant stories.
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.