My suggestion is to start with creating Family groups called UserObjects.
You will need to create a family group for each type(Sprite, SpriteFont..) whatever is needed. make sure that your UserObjects has all required data. Then loop through each UserObject turning each object into a JSON into an array.
Then you can use the the JSON output of your array to send up to your server.
The next job is. You need to itterate throug the objects and place them in the level.
Otherwise you can't actually create a proper URI out of data. You just have to it as an AJAX.