How do you allow mutliple bank characters to be listed? There is probably a very simple way to do this, believe i am having a brain skip on it though.

This is the way my guild does it:

In game, make the "Player Note" contain the words "Guild Bank". You do this for all of your guild banks.

Then in your "Roster Config" > "Guildbank" settings:
Banker search text: "Guild Bank"
Banker search field: "Player Note"

Then you update your roster and voila!