Yep! That works, but it's essentially the first option ("How to sign a JSON object") but with JSON as the outer serialization format instead of a comma in the m

Yep! That works, but it's essentially the first option ("How to sign a JSON object") but with JSON as the outer serialization format instead of a comma in the middle. You also correctly identified why that is different from the other schemes: they don't change the structure of the outer object.