Hi @ROHPU
The loopback connector building is something that will take time. There is already a standard connector available which you can check and see if that is enough for your use-case.
The idea of loopback-connector is basically that you can manage ISC user levels etc are as entitlements itself and with this you can even connect to your non-prod ISC tenants and then grant access to them from your prod tenant.
This way if you generate the campaign the from production tenant , then you can even review the user levels assigned to the admins in test tenants or dev tenant via single campaign.
There are lot many reasons to implement it and depending upon the use-case i have seen customers deciding to either build their own connector or use out of the box connector itself.
You can use below document for more information.
I hope this helps.
Regards
Vikas.