I would like to be able to tell at a glance that I'm coming across a clan leader on the overworld map, or that I've captured one. Usually there specific things that you may need the leader of the clan for, ie marriage proposals or convincing a clan to join your faction. With so many nobles in the game, I sometimes find it hard to remember which ones are clan leaders, even when seeking them out. Same can apply to faction leaders, especially after one of the original leaders die.