@dasralph: I am currently pushing Kotson-2.2.0-beta1 on Maven Central (should be available in a few minutes). It features the read / write stream API that you told me about (https://github.com/SalomonBrys/Kotson/tree/2.2-beta#setting-custom-readers-and-writers).
Could you have a look, maybe try it, and tell me if there's something missing or not working ?