Project status: nearly done with my LevelGraph refactoring, now I have a version that uses async iterators and promises and that should be much easier to extend with support for statement-level annotations and other neat features (without breaking stuff)
Despite the complete internal rewrite, and the move to async iterators instead of streams and promises instead of callbacks, it actually doesn't break any of the existing API; it's fully backwards compatible (and still passes all the original tests aside from some internals tests).
The new features probably won't all be supported with the old API, but internals improvements will.