I loved that the empyrean items like Briareus Helms and Sobek Skins were made stackable, but I would also love to see certain craftables made stackable as well.
Items such as elemental beads and ores would be very convenient to have stackable, especially now that they're available in such abundance from Abyssea, and a lot of the time they end up NPC'd rather than sold on the AH, or even dropped to save space.