1) Well, actually is the bracket and the comma. We're using simplified json in bindings.json. All bindings could be in one line.
2) The engine part is only for when we need to convert an schema object to "something" manageable by the engine or libgdx. E.g., Transform is converted to TransformAction, which contains the logic to apply the action, but Behavior is just a map that it's read by SceneElementActor. We don't need a wrapper around it since its logic is processed in SceneElementActor.
3) Yes