What I have understood from your question is that you are creating a game where a player will place objects in the world and then will share that world with other players. Am I correct?
AppWarp has a sendUpdatePeers method to send binary messages. You can serialize any object and send it with this method. The maximum limit of message is 1024 bytes for sendUpdatePeers.
I would recommend you to instead of serializing objects and sharing with other players you can share actions. Suppose when a player places an object, share this action i.e. a message representing which player placed what object at which place. You can create a JSON message for this. If you want players to create the maze all at once and then share it, you can create a JSON containing list of names of all objects with position and rotation and share it with other players. Or better if you can organise all objects in the world in a grid, then you can represent the world with a 2D array with each element in the array describing the type of object. This will make messages small in size.