Sometimes we have MNCs with their local branches in different countries and they don't necessarily have the Global Accounts every time for the reasons due to the Organizations Internal Structures, Geographical Locations, Project Execution structure/methodology. The users do get transferred from one account to other, but their BBID cannot be transferred or moved and needs a back-end BB support for every single case.
Please make a provision to the Org-Admins to not only deactivate but also delete a user so that with the mutual consent of both the Org-Admins a user (BBID) can be shifted from one account to another.