For now I don’t think the forum is a good place to act as a “marketplace”. I have to think about handling these types of requests first 
Yes, I’m working on a refactor which will make it a lot easier to re-use codecs. Until then, please know that if the code is executable by the Otto JS engine (used by ChirpStack), it should be fairly easy to create a wrapping function around the TTN / TTI codec to match the function signature.