We need an AH

[Tsuga]

That's it? You're just not trying hard enough.

Notifications of a sale
Notifications of a cessation of vending
History of recent buyer/sellers
Separation of NQ from HQ versions of the same item
A search feature (Not in FFXI's version but it would certainly be a good adaptation)
Not putting your storage space on hold while you sell something
Being penalized for selling items of the wrong category, even if you don't have a choice about it

All of this, plus AH would alleviate the ridiculous retainer limit per ward that prevents you from even being able to sell your wares, in a lot cases.