Fortimanager deployment on existing Fortigate network

Hi 

One of my client bought new Fortimanager to manager their 7 Fortigates which are in production. I tried to keep all 7 firewalls in a single ADOM with their own policy package. When i import policy package from Fortigate to Fortimanager, if there is any conflicting objects from policy package imported from firewall 1 are replaced by newly imported policy package objects. I understand that Fortimanager single ADOM can have one database that's why it is overriding. I would like to have all firewalls in single ADOM with their own policy package and objects as currently configured on Fortigates. Address objects should not be overridden. is there any way to achieve this? or do we need to tidy up conflicting address objects from all 7 firewalls?

Thanks