Solfernia Well, as you're sharing a guild storage, you're automatically creating this risk. You have to understand that this is a risk made by you, allowing people to use your storage. This requires trust, and if you can't commit to that, then perhaps guild storage shouldn't be shared among your peers.
I'm not trying to argue your way of playing, but you're slightly asking for a change that really involves your, and your guildmates short comings. Now, I agree with Dreamfall, but I think this is a self-created issue, which I think everyone should be aware and just be more careful. It's really that simple. 😃
I hope we get dreamfalls change, so you can at least feel at ease about your guildmates, but maybe you need to vet them to reassure yourself they are worth trusting to have accessibility to the storage.