I’ve actually just created a ChatGPT binding: https://github.com/openhab/openhab-addons/pull/14809
As explained in the PR, I see a fairly simple, yet neat use case: I have many announcements through TTS over the day and they appear to be coming from a machine, since they are always exactly identical. With the ChatGPT binding, I see a chance to make them much more natural by having them formulated by ChatGPT, which means that they will be different every time and I can simply pass in “raw” information that I want to be informed about. Let’s see how well that works and what other ideas other community members might come up with. 
P.S.: I agree with you, though, that ChatGPT isn’t (yet?) suitable to take control of items - that’s why I decided to not implement it as a DialogProcessor, but rather as a binding for text creation.