If SE implements linkshell common storage in some fashion, regardless if it is a retainer, a vault, or a chest, I would like to see this as a 'purchasable' option for a linkshell. Given what very little know is known about Grand Companies, I could see purchasing this as an option once enough GC quests are completed and enough Grand Company marks (or whatever they may be called).

This leaves the option of having "simple" linkshells for socials, whereas a group that wants a more full-featured guild the ability to work toward it.