There is not a way to specify a raw scan when creating a remote
scanner via HBase REST API. The backing server implementation does not
carry arguments that toggle raw scans, but it could be added as a new
feature.
Please file a feature request over
https://issues.apache.org/jira/browse/HBASE for this.
The existing service-end implementation that builds the scanner on the
REST server is at (upstream)
https://github.com/apache/hbase/blob/master/hbase-rest/src/main/java/org/apache/hadoop/hbase/rest/Sc...