I hate random suggestion posts, so I'll make one I guess.
We all have inventory issues, and SE has constantly reminded us that it's pretty much our problem.
So here is my suggestion, (If it's been made before, sorry)... It also comes from FFXI (Sorry ffxi haters).
Key items for full armor sets:
FFXI had a system where you could farm the full set of an armor type (rare armors, think green / blue) trade that full set to an npc and get a key item ticket that you could trade in and get that full set back at any time.
Ex.... Trade in full set of High Allagan Fending set, get key item "High Alligan Fending X Ticket"
We all have more than enough key item slots to hold a few of these tickets, and it should reduce server loads by reducing 5 items down to 1.
It's simplistic, and I don't know if it could be implemented. But I would like it.
** Edit: From FFXI
FANTASY XI Development Team (24/3/2005)
In the previous version update, a new service was added allowing players to safely store full sets of artifact armor for a small fee. Due to the positive feedback regarding this new feature, the development team has decided to expand the equipment storage service to include over thirty new sets of various low-level armor and clothing. After trading a full set (consisting of 4 to 5 pieces) to one of four NPCs located in each of the major nations, players will receive a claim slip that can be presented when they wish to have their armor returned.
Whether for level-restricted orb battles, Promathia missions, or for raising support jobs, low-level equipment can eat up a lot of room in a player's Mog Safe. Utilizing this feature will make it easier to store and retrieve space-consuming armor sets, while leaving Mog Safes open to hold more important items. The days of throwing away sleepshrooms to open slots for your silver gauntlets are over!