The goal of the crypto and KMS plugins is to provide a pluggable interface for Cryptographic operations such as Encryption, Decryption, Signing and Verification as well as keys management operations usually offered by a KMS (Key Management Service).
Aries Agents should be able to plugin a Crypto module and a KMS module and use their services regardless of their detailed implementation. This will help integrate crypto operations as well as manipulating and querying keys in an agent with minimal change.
Tink, a library created to make crypto easy for non cryptographers, is a strong candidate that offers pluggability of crypto operations and supports integration with multiple KMS solutions like AWS KMS, GCP (Google Cloud KMS) and Android Keystore KMS. It supports multi languages including Go.