I also think that using someone's good solution is better then inventing a new idea from scratch.
ZOS may use an example from SWTOR , the vaults idea, and their customer support - seems helpful when reading this:
Guild banks and scams
Given the customizable nature of the Guild Bank vault access settings, we hope that Guild Banks will be well protected from unscrupulous players. However, we also recognize that the availability of these settings are not protection enough against some players who use tactics like social engineering to gain increased access to Guild Banks. We sympathize with any Guild who find themselves targeted in this manner, and our Customer Service team will be happy to assist any Guild Leader who finds themselves in this situation.