Very cool stuff!

This did catch my eye, however: https://github.com/creationix/rx?tab=readme-ov-file#proxy-be...

While this is a neat feature, this means it is not in fact a drop in replacement for JSON.parse, as you will be breaking any code that relies on the that result being a mutable object.

True, the particular use case where this really shines is large datasets where typical usage is to read a tiny part of it. Also there is no reason you couldn't write an rx parser that creates normal mutable objects. It could even be a hybrid one that is lazy parsed till you want to turn it mutable and then does a normal parse to normal objects after that point.