JSON is nothing more than a rendering and fully supported by libraries such as the Apache Java XML2JSON library we are using - bi-directional seamless transforms.
There is nothing need to do here. NIEM does JSON, and JSON does NIEM, and its completely interchangeable. CAM demonstrates that as a reference implementation and anyone else can easily do this too.
CAM Reference Link: https://www.youtube.com/watch?v=CeDbY0FSX3Y&list=UUHGjVfq4Rm-CC2ClFS2cD6w