Hot reload in Java is still a crucial part of my workflow for modding Minecraft, but it doesn't have the other direction where an action in the game could alter the code

Ah, fair. Seems that is probably more applicable to image based development than it is typical batch processed source files? Doesn't seem too strange to have your code editing a data file, for example. No reason you couldn't treat your source as a data object, in some sense. Though, I'll note Common Lisp explicitly warns against editing literal objects. Such that I'm assuming this was considered and largely agreed to be a bad idea. :D