Magento Multi User Account

You will have to enhance an already developed extension in Magento. I had created a freature which allows to use, register and login with nicknames instead of email. You will have to enhance this feature with permission to use multiple email accounts and implement it on a client installation. Lets say a company has just one e-mail address. But they have 5 employees who all need their own account with use of this single email address. Create and install it on our server. Budget is strictly 40-60 USD