Major Description
There should be some level of protection against inadvertent data loss when issuing these commands when replicationFactor is 1 - deleting a node or a replica in this case will be equivalent to completely deleting some shards.
This is further complicated by the replica types - there could be still remaining replicas after the operation, but if they are all of PULL type then none of them will ever become a shard leader.
We could require that the command should fail in such case unless a boolean option "force==true" is specified.