Hi Joyer
It is possible ,you need to deploy GRC Portal content on the Portal server and then follow installation guide to integrate GRC with EP by creating all the required connectors.
Once done you need to configure EP connector like any other connectors for all the actions like ECC.
Also you need to upload Portal Roles/Group definition in GRC system.So when you try to create request your Portal system should also come in the dropdown for provisioning action.
Other way which we did is by creating dummy business roles and map this business role with all technical roles from all the system in the landscape which user should have like 2 roles from ECC,1 Role from CRM and 2 Portal Roles/Groups from and once that business role is assigned to the user the whole package of technical roles will be added to the user provided Portal Connector is available for Provisioning.
Regards
Pradeep