in a DR secnario where a site is complete down, the ability to reverse SR replication via powershell is not applicable
Currently with Storage Replica, you can reverse replication via powershell as described here (second form the bottom): https://technet.microsoft.com/en-us/windows-server-docs/storage/storage-replica/storage-replica-known-issues
However, in a DR scanario where the initial source site/node is completely down, the ability to reverse SR replication via powershell is not applicable.
Nathon Sweetman commented
If Node A is primary and Node B is the replica and Node A has a critical shutdown, you can reverse replication on Node B, this will allow the replica on Node B to become available, and prevent Node A from replicating to it when it comes back online. Once Node A is back online run the exact same reverse command you did on Node B and it will update Node A and allow Node B to replicate to Node A. That being said it would be nice if the config was stored in AD so that Node A would pick up the config change when it came on line and queried AD.
That's a true statement, but I don't understand what you want changed via this feedback request. You would remove replication if truly gone. If you switch and the other server cannot be contacted, you are warned but can continue.