Unfortunately, the community cannot be trusted to treat such a feature with respect and SE would never put in the time and money to moderate it.

However something akin to ESO's Antiquities or WoW's Archeology could be fun. Fun optional ways to interact with the world, maybe unlock lore or treasures, could even tie it into Chocobo Digging. But, that would require SE to refresh old content and I'm pretty sure they'd rather just update the Mog Store.