As it is now, pretty much everything can be gathered by the 3 existing DoL classes. If there were to be a new class, why not an archaeologist who could gather things already existing but now have been broken down by time/the elements/aether/you name it?

I was thinking that the main thing to gather here would be fossils or old technology that can no longer be made (allagan or Garlemald technology). Fossils could be used in DoM weapons: if the beast or person had a cruel death -> great aetherial energy for uses in BLM weapons and if the remains had a blissful life -> weapon for WHM. The technology finds would be used in new DoW weapons.

With fossils you could have skills that makes you more likely to find remains that had a blissful life or a dreadful death. The better the life or the worse the death would be HQ items.

It would also be cool to dig down and find out more about the allagan empire and the different eras. It could even begin in Saint Coinach's find in Mor Dhona.