You can create your own emitters, there's info in the docs on how to do so. My team built a custom TypeSpec emitter to output a SDK and set of libraries
I'm the TypeSpec PM at Microsoft and I'd like to learn more about your use case and experience building a custom emitter. Are you willing to chat about it? If so, what's the best way for me to reach you?
There are a few emitters in our standard library - OpenAPI 3.0, JSON Schema 2020-12, and Protobuf. REST client and service emitters for a few languages are coming online now and should be ready in the next couple months.