Before we had structs (which are not dynamic at run-time, so you can't do what you are looking for) I used to use Array objects (in conjunction with Enum_Lists, but they are static as well) to do that sort of thing.

You might write something which added items to such a thing based on the received JSON, but in truth, the best way to do this would be by using the cJsonObjects, which are designed for the purpose.