Drupal single user, multiple civicrm memberships, editable details: What's a good logical approach to integrating them?
If you set up your membership type so that it provides an 'inherited membership' via the 'employee for' relationship, then the Employee will have a permissioned relationship over the Business, and can therefore access the address details etc for the Organisation via their Contact Dashboard.
Secondly if they are logged in then the employee (or primary contact or whatever you need it to be) can have 'permission' on a webform to update more details about the Organisation if you can't give them enough access to fields via Contact Dashboard.
Does that move you towards your goal?