Umm, you can do basically all of this, today, with Home Assistant and a handful of add-on apps.

I use a local LLM with it, but you can use a hosted LLM if you like.

The core home automation stuff can run on a potato. The LLM just writes new automations when I ask it, or acts as a natural language interface.

I use a pretty small 4B parameter local LLM, on a fairly modest mini PC. It doesn't take a frontier model to do that kind of work.