The address composite forms are used to quickly edit all fields of the address and present all of the fields together in a visually appealing manner. The trouble is that you can’t customize these forms at all. You can’t add or remove fields so when I wanted to use an option set for a customer State/Province field, I had to figure out a workaround.
Luckily, business rules can be applied to all forms of an entity so I set up a rule to hide the out-of-the-box state at all times. Then my custom option set state field is placed on the main form. I have another rule that sets the out-of-the-box state field to the option set value so that the full address appears correctly. In the business rule, just remember to set the scope to entity so that it applies to all forms.
