I have a client that upgraded to enterprise from professional and because of this, there are emails that are sitting in the original account (now a business unit) that we cannot move to the new business unit. It is currently only possible to associate assets to business units that were created after the business unit was created. Today, assets would have to be "recreated" and not existing in order to be associated with the appropriate business unit.
We would like to be able to retroactivly associate assests to business units to ensure they are associated to the correct domain and permissions.