As a disclaimer, I work on the BigQuery team, but I wanted to point out that there is now support for transferring data from S3 to BigQuery: https://cloud.google.com/bigquery/docs/s3-transfer-intro
Another item to consider is that BQ now has ML (simpler) models built in, further reducing the complexity of your pipeline: https://cloud.google.com/bigquery/docs/bigqueryml-intro
If you are not on GCP, then I’d consider AWS Athena for querying the parquet files, but you still have to structure these efficiently beforehand.