I would like this if it was like a custom levequest option, where the player can request specific items, and could offer items (or optional items), as well as gil, as a trade. It would also be good to able to leave an optional description with the listhing. This would allow the sale/trade of sets of items, as it's not always gil that I'm interested in. Custom levequest rewards could be taken out of the retainer inventory. Perhaps it could also have an option for the custom levequest to be completed multiple times, if sufficient inventory is available for rewards.

It would also be nice if you could limit the people that could access the requests, like FC-only, LS-only, or a list players. I manage the airships for my FC, and it's not always easy to get other members to gather materials for me. It would be nice to have some sort of reward incentive system in place to get them to contribute more, and it would be useful if we had the option to limit these listings to a specific groups of people.