I find a certain confusion in in the use of username. The client identifier in the Mail and Web setup pages is set to the username of the account. If you had an additional field, say, Account Name, this confusion would not occur. A company could then have many accounts. I forsee a problem where one person is responsible for many accounts and sites. Multiple usernames is a major headache for a user and causes a lot of login problems. Therefore a CP user should not be tied to a single account but after login should be able to select the account in question.