phpBB main accounts with subaccounts

Mod for phpBB (2.0.20) that changes the way users log into the system. Shouldn't be too difficult for someone who's familiar with phpBB and PHP. Here's how it will work: Users create a main account that uses their e-mail address as their user name. This account will not have access to the message board, but may still send private messages. Once a user verifies the main account through a link in their e-mail, they may log into the system. From there, they have access to a control panel. The control panel will have the following options: Create, deactivate sub accounts, or log into the system with a subaccount. Subaccounts will be subject to the usual phpBB controls. From the ACP (admin control panel), subaccounts can be deleted, deactivated, or reactivated, and may also be transfered between main accounts. Additional functionality will be required in the future, and this will require us using the winner of this bid for still more work.