I have a few quality of life recommendations regarding inventory, the economy, and general gameplay within FFXI.
Auction House
The auction house item quantities have dwindled greatly over the years, and I can think of one reason this is the case in particular...
The item posting limits at 7 per character are no longer a viable option. With the largescale downsizing of active player populations across most servers, the Auction House system is slowly being choked to death.
An alternative to increasing the item posting limit would be a more investment intensive combining of Auction Houses across groups of servers, thereby allowing for an overall larger economic hub. I can see where there may end up being potential conflicts of interest towards the business model in this case, therefore I would consider it a more drastic course of action, reserved until servers start facing severe economic downturn.
Delivery Boxes
The delivery box system can be frustratingly slow, we all know it, and thus far we have all accepted it. This is not however the only be all end all option.
Expand the delivery box window to show more than 8 slots... Even in SE's other MMO properties, delivery/mail systems have a more traditional "View all incoming mail, and select which you want to access from the list" approach. Understandably the base engine in FFXI is incredibly dated, however, modifying the existing window images to accommodate more slots for an already existing larger, albeit invisible to the players, inventory that sustains a limit of 128 queued inbox items should be far less of an undertaking that should be relatively feasible with the current development teams still allocated to FFXI. Not having to spend the countless cumulative hours of agony cycling delivery boxes, especially when transferring items between a player's own characters, would GREATLY alleviate the stressful interactions with the entire system overall.
Additionally a far less important, but I think, valuable tool that currently does not exist would be the ability to send a player a physical note via the delivery system... I can't tell you how frustrating it can be to try and catch that one particular player you wanted to contact when they're not online, due to a difference in play times. This has been a more and more common occurrence as the player base for FFXI ages up overall and is engaged in increasing IRL commitments.
Passive Job Traits
Could we please add a I, II, III, IV, etc... identifier for job trait tiers when viewed via the abilities menu? It seems like such a simple concept since the traits themselves must have an inherent value difference encoded that makes them distinguishable, and therefore only would need their respective displaying text for each tier within the menu itself to be amended. This way the highest achieved value is more easily understood and visible thereby eliminating the need for most players to access outside of game reference materials and player guides to understand the invisible potency levels of their available traits. It would certainly be of great use when weighing sub-job or blue mage spell trait combinations. It's incredibly frustrating to have to reference a guide on each individual trait via outside sources, only to have to measure and calculate how one obtained the trait, how many blue mage points for a particular trait are equipped, and in effect when a new threshold has been achieved.
It may all seem trivial, and par for the course for the entire FFXI experience that we've all come to know and love by now, but I personally feel that a matter of a few simplified tweaks to basic player UI elements can make a world of difference in overall enjoyment for player (and subscription) longevity.
Thank you for viewing my ideas, and I hope that you will please take my suggestions under serious consideration for future updates!