Currently the product does not allow you to connect to external AR service, querying a external domain’s Service Connection Point. The AR Management Shell will allow you to specify and connect to a specific external AR service, but this does not offer any failover capabilities if the service is down.
This is by design. An enhancement request (TF00756312) has been created detailing the feature described above.
The product team will evaluate the request and this feature may become available on a future release of the product.
Please refer to this article for updates or contact support referencing the Enhancement Request ID: TF00756312.