Dual encryption in Aurora postgresql/babelfish

We are working on migrating SQL Server to Babelfish. The customer has Transparent Data Encryption (TDE) enabled on their SQL Server, plus column encryption on a few columns. Additionally, their EBS storage is encrypted using AWS Key Management Service (KMS). The customer is expecting the same kind of dual encryption in Babelfish/PostgreSQL. However, my understanding is that the maximum encryption that can be provided in Babelfish is storage encryption plus column encryption using the pgcrypto extension. Is there anything else that can be done to meet the customer's requirements?