I believe that you are the second person to ask about this, but I cannot think of a way to handle this without rewriting the extension for the third time - at most I can add an option to alphabetically order fields and/or a special field that you can set to an array of keys to control field output order, so something like
{ "a": 1, "c": 3, "b": 2, "$$order$$": ["a", "b", "c"] }