The whole shard rebalancing problem is solved if you have an acceptable disaster recovery solution in place, which I'm assuming the author doesn't if they're complaining about have to keep around the raw copy of their data to be indexed.

My team has an automated workflow that runs once a week. It creates a new cluster, re-indexes from source, starts taking customer traffic and then deletes the old cluster. The shards stay balanced, and we can recover from a total cluster failure within about 6 hours.