I know I will get downvoted for this and people will just say "you're doing it wrong" or "the library wasn't designed for that" but I still think it would be really helpful for some people if the source of the data to swap out could be retrieved from parsing the response data as JSON and grabbing a certain named key.

Yes one can add a callback function to parse the data as JSON, do error handling etc. and then swap the text/HTML, but having that built in to a hx-foo attribute would be a lot easier.