However, I think there's a sweet spot where you could implement a fairly nice boilerplate/framework that would be an 80% solution to the problem which would be a vast improvement over the current state.

The missing 20% would be language specifics and that would be either solved by forking the boilerplate code or writing some kind of callbacks for discovering references given a root object.

edit: Additionally, there's no simple example of using a GC with LLVM. It would be very helpful if there was, for example, a GC'd version of the Kaleidoscope language used in the LLVM tutorials. Even a trivial Lisp-style cons/car/cdr object system coupled with the simplest possible mark'n'sweep GC would be good.