It sounds like you think adding a conversion at the start is difficult and cumbersome, but it isn't if you use a good serialization library. E.g. with the Rust

It sounds like you think adding a conversion at the start is difficult and cumbersome, but it isn't if you use a good serialization library. E.g. with the Rust library serde, you just define the shape you expect your JSON data to have and plop a #[derive(Deserialize)] on it. Boom, fully failsafe JSON deserialization into the type.