I like the idea, but it has about too many bad issues that would need to be solved first:
guild leaders can manage this already using their fg, just keep track of who has what
additionally individuals can just save and it equates to a bank
you need an incentive to deposit like interest when others borrow, or fees to those now contributing
BL: too many holes to fill for a lot of effort on the site, when we could all track it ourselves anyways