Multiple Emails For 1 User

Hello,

I am building a site where I am offering sponsorship advertising packages. Some of the sponsors I work with are from large companies who have more than 1 person in charge of their advertising. Is it possible, with this plugin or an add-on, to apply more that 1 email to a user account or possibly have sub-users under a main company account where all can access the level use as the company account? Other solutions are welcomed to reach this goal. I appreciate your time and look forward to hearing from you.

Best,
M. Baker