The save system is meant to be modular, flexiblie and extendsible at its most on every aspect, such as Storage API, Encryption API, Serialization API, ... Follow the below instructions for creating or extending the system for implementing your own feature or adding your own requirements to the system.
You can extend or create your own storage by extending the StorageBase class, for more information take a look at How to Create Custom Storage.
You can extend or create your own encryption by implementing the ISaveSystemEncryption interface, for more information take a look at How to Create Custom Encryption Algorithm
You can customize the serialization of objects by using the Converters to implement your own process, you can do it by extending the ObjectJsonConverter or JsonConverter.