I would enjoy a way to add a nickname to party members. I know it may make the interface too large, so maybe it replaces the first name. I want it for immersion and to create my own stories. I also have terrible memory so it helps me remember my favorite characters. 

On the Roster if you click on the name and go to the Roster card you can click on the pencil Icon and add your own names (Nicknames)
Hopefully this is want you are asking after!