Setting is as easy as sending a message to the named object with the set or message functions, but retrieving the current information is much more difficult. One idea is to script a [grab] object into place and connect it to a [message] box and back to a dedicated inlet of your [js] object. If you only need this to work in a patching environment you can even parse the JSON text of your patch as demonstrated in this article. However this won't work with anything other than a maxpat file so if you need it to function in a standalone application this method will not work.
I think you might ask C74 directly, and they should really adapt a bit max objects to your goals in next incremental max version, come on!, what you're working on ( http://cycling74.com/forums/topic.php?id=28177 ) is just the future of max!