I am not sure I understood, can you show your scene ?
If I understood correctly you want an viewport to show your current scene in a different way, I use it a lot to show for example, a complex mini map, with different texture, if this is the case, you just create an new scene similar with your current scene and with different texture, render it in the viewport, and remotely move the objects to give an felling of it to be the same scene, even as its not.