thank you for building an amazing product!
I suspect cloning OpenAI's API is done for compatibility reasons. most AI-based software already support the GPT-4 API, and OpenAI's official client allows you to override the base URL very easily. a local LLM API is unlikely to be anywhere near as popular, greatly limiting the use cases of such a setup.
a great example is what I did, which would be much more difficult without the ability to run a replica of OpenAI's API.
I will have to admit, I don't know much about LLM internals (and certainly do not understand the math behind transformers) and probably couldn't say much about your second point.
I really wish HomeAssistant allowed streaming the response to Piper instead of having to have the whole response ready at once. I think this would make LLM integration much more performant, especially on consumer-grade hardware like mine. right now, after I finish talking to Whisper, it takes about 8 seconds before I start hearing GlaDOS and the majority of the time is spent waiting for the language model to respond.
I tried to implement it myself and simply create a pull request, but I realized I am not very familiar with the HomeAssistant codebase and didn't know where to start such an implementation. I'll probably take a better look when I have more time on my hands.