I would like to understand you POC (what exactly you are looking for ?).
You can have some script for blueprint to add node dynamically to the cluster. Pls refer -
I have earlier worked on EMR. You can check for AWS EMR which can be used for autoscaling hadoop cluster.
Refer to the below link to see how you can add/delete nodes in ambari managed HDP cluster.
This link is for Ambari-18.104.22.168, if you are using older version of ambari, the same can be found under docs.hortonworks.com.
The response is Cloudbreak: http://hortonworks.com/apache/cloudbreak/
It can meet the requirement in either public clouds or private clouds built with OpenStack. This type of elasticity you are looking for is the driving requirement for Cloudbreak. Additionally, you could consider Hortonworks DataCloud which is built in top of AWS using Cloudbreak.
If any of the response in the thread helped, please vote and accept best answer.