Storage in DDO is a major problem.
Ok so we have to grind for 50 million years to get all the favor to unlock the extra inventory slots and bank slots. Once that's done, you quickly realize that it's still not enough. Especially when you have full character slots and save loot for them or your guild. Storage in DDO is simply inadequate.
Why not allow members to purchase mules and wagons/carts to carry their loot?
Imagine for a second that you could buy 1 mule and if offered perhaps 60 slots of storage.
You could then buy a wagon/cart for the mule, giving an additional 60 slots of storage (or more).
If you hitched two mules together you could have a caravan (200 slots) etc....
You wouldn't need to graphically show the mules or carts in-game, just have them setup/displayed like the backpacks.
While in a quest your mule/cart would be inaccessible, however once done the quest and outside; it would be accessible.