This should be set up very similar to the Addresses or Contacts tabs. We should be able to define shipping default methods and have a place to include their shipping account number for that method.
If a customer has given us their UPS or FedEx account number we currently have to put that in one of the Custom tab fields.
Under user defined settings you can add multiple shipping methods with account numbers
This is a terrific idea! There isn't any place to store multiple methods of shipping for a single customer or account numbers.