Okay. I know I voted and made a comment in the past (like the third or forth page) of this thread, but after waking up after a night of drinking, I will make an amendment to this suggestion.
When you click on "Transfer" when you have a "Vault", it automatically "LISTS" all of your "Guild Member(s)" that currently have an "Active Vault", also the "LIST" is their "Username" and when you click on that "User" and "Transfer" an item, YOU don't need to know the "Users ID#" as it is ALREADY applied because they are "IN" your guild and have a CURRENT vault etc.
Basically... you click transfer and the drop down box automatically lists ALL guild members with a current Vault to APPEAR, all you need to do is, "click that USERNAME" and you put the item in the Box and it automatically goes to that user IN YOUR GUILD (Guild member).
If you are unsure of what I have written, let me know what you don't understand and I will try to explain it better. As for those that do understand where I am coming from, maybe they could word it better for those that are unsure.