I'm actually not sure what those are for, but I was wondering if it's not already implemented that if you click on a trace of battle that you could get an item that was supposedly dropped in battle. Maybe potions, or at rare times gear that might or might not be slotted. And then if these traces of battle could be in every map with items suited to the relative level of the mobs in that map.
It's used as sidequest for the 6 first jobs I think, never done them, but you can probably google guide. Don't plan on making any custom modifications to those quests.