This involves easily adding a peer (or removing) from a running cluster. `ipfs-cluster-service peer add <maddress>` should work and should update the peer set of all components of all peers, along with their configurations.
This involves being able to pin an item in, say, 2 nodes only. Cluster should re-pin whenever an item is found to be underpinned, which means that monitoring of pinsets must exist and be automated.
* Tests (https://github.com/ipfs/pm/issues/360)
In the context of the Interplanetary Test Lab, there should be tests end to end tests in which cluster is tested, benchmarked along with IPFS.