Can I set a blueprint actor as a component for another blueprint actor?

That is true but you can get the variables of the child actor in the event construct of the parent and expose to use in the editor outliner.

like any other component

but back to the @ecksdeeeee question, maybe the best solution is have a hidden paper inside the box, that paper copy the real paper propieties and turn visible when interact, do any change u want with the fake, when the interaction ends copy the fake propieties to the real.