So I get the Guild storage is mainly for Guild wars, to contain guild related items. Why not open it up to other Items, maybe lock all items placed in guild storage to only be sold by the guild master sending the funds only to the guild funds. IE: Guild member farmed got a low level boss weapon for a class they don't play or even a spare boss weapon box. Instead of selling they lock it in the guild storage (giving it a guild brand) so another member can use it on a loan. The recipient cant sell or discard it.They can enhance/ repair it but it's guild bound, if they leave the guild it returns to the storage. I believe this could make being a part of a guild more of a team effort than a solo grind for new players. 

Now say a player just vanishes or goes AFK for good or stops playing. Maybe as another feature you could give two ranks the ability to recall Guild brand items back to guild storage remotely. The ranks could be restricted to the Guild Master and the Quartermaster. 

Thank you for the suggestion! I added it to my report, and will get it sent up today! :D