payment-processor for multiple (bulk) memberships
A couple of thoughts:


The data model where Payment is recorded from a Different Contact in CiviCRM (for Membership payments) does indeed exist natively in CiviCRM. You can use this to record a Payment From the Organization.





The data model where if an Membership Organization has acquired a Membership -> Memberships can filter down to a specific number of Individuals who have a current/specific relationship with that Organization also exists natively in CiviCRM.





The data model where the Contribution is recorded at an Individual level and subsequently the Organization is also invoiced for it - that's highly unusual as it will lead to double financial records. If the Organization is paying for the Membership but the Individual is paying/perhaps this would be a reimbursement from the Organization to the Individual? 
(preface - love Webform CiviCRM module) - if you're on Drupal - you can have a single Organization purchase memberships for any number of Individuals on one page; The monies will be recorded in that Organization's Contact Record - all Individuals will get Memberships; Add in Soft-Credits for bonus points.