Link Organization Contacts to Individual Contacts (more strongly than via "Relationships" )

Required:
Give Organizations the ability to log in via a Primary Contact
-link each Organization with a Primary Contact
-give the Primary Contact the ability to edit the Organization
-allow the Primary Contact and the Organization to have the same
email address (link them using email addresses?)

Ideal:
When Organizations are created, allow the creation of contacts
linked to that organization without requiring that contact to sign in
or already be created.
These contacts could be linked by "Relationships" to their contacts,
but ideally the Primary Contact would have the option/ability to edit these
contacts as well