Well I have started testing the so called composite Control, this control is just a scene render pipeline which makes it very powerful. Basically you can setup any type of scene and point fbo textures to an object. All the feature of scenes are the same (culling etc...), its just a scene.
Anyway the image below shows 2 scenes that connect from a quad in the composite scene to the Viewer scenes fbo output texture. The border around the quad is only there for debugging.