That kind of inflation is just a side effect of format encapsulation. You're representing a path format inside the JSON format, both of which need to escape their delimiters if they're to be taken literally. I still think a single consistent escape character is cleanest.

The same argument applies when I have any defined escape character or delimiter that I want to use as a literal.

I'll admit it's less human readable if you have a key `\/` but I can't think of many good reasons you'd want that as a key, which is what makes them good escape characters and delimiters.