This would be Guild Hall upgrade and each player would pay a one off fee for their own residence (say 1K).
The residence would be tied to an account and shared between characters, as with Xunlai boxes. It would cease to be accessable at times the player isn't in a Guild with a hall and appropriate NPC, but nothing would be lost.
This idea occured to me when I recently started playing Morrowind again and I couldn't believe the amount of stuff I'd stored in this one little room of my stronghold - drawers filled with clothes, a floor stacked with armour, crates of enchanted weapons, tables filled with gems and a bed covered in broadswords and staffs! And I didn't spot a single thing I could have lived without.
