At this time there is not a way to STOP and EMR cluster in the same sense you can with EC2 instances. The EMR cluster uses instance-store volumes and the EC2 start/stop feature relies on the use of EBS volumes which are not appropriate for high-performance, low-latency HDFS utilization.
The best way to simulate this behavior is to store the data in S3 and then just ingest as a start up step of the cluster then save back to S3 when done.
Hope it helps.
If you want to maintain the same dns, you can use the API/CLI to update the elastic cluster.