Ref Doc - Splunk Add-on for GCP Docs
Currently, the Cloud Storage Bucket input doesn’t support pre-processing of data, such as untar/unzip/ungzip/etc. The data must be pre-processed and ready for ingestion in a UTF-8 parseable format
For feature enhancement requests you should visit https://ideas.splunk.com/ and if there is no existing idea matching with your request/idea you should raise a new idea.