Is there a way for a supplier to register without creating a User ID?

During the supplier registration process, the supplier enters their contact information along with user ID and password for the new account. However, we would like to control the User ID for the new users. I was thinking this could be done by creating a new user after supplier registration approval, assuming that no user is created automatically during approval. Is there a way to "turn off" the Contacts train stop? or to not allow entry of the User/Password during new supplier registration?

The Supplier Change Requests let you decide which trainstops are used, but the New Supplier Registration train stops are not similarly defined on the template.