Enable Guild-bound Items
Allowing items to be guild bound, making them unable to be dropped, upgraded further, NPCed, traded, or put into any personal storage. Each item could have a fee of 300k - 500k or so to become guild bound. Anyone could bound the item to guild via NPC, and only guild leader can unbound them. The fee would be re-applied if you wish to unbound an item and re-bound it. A list of items could be displayed to any guild member with the command @gitEm or something similar, that displays what character has the item. The guild leader could recall items to guild storage (or personal inventory if that's easier) with the command @recallitem, or something similar.
This could help players that need to borrow gear for PvM or WoE without having to worry about them being online to get it back or anything happening to the item. This could help prevent any distress waiting for someone who is borrowing an item to come back online, and ensure the item's safety. Furthermore, it would result in a good zeny sink for the server.