The only workaround I can see, is to open up a new scene in the "inches scale"(Small:30in) and create an Isometric camera. Then copy and paste that camera into another scene(if the scene is scaled larger).
Note: Another thing to watch out for, is that renaming a camera(under the selected camera/General tab/Name: ),
may switch the Rendering Camera back to Camera 1 in the Render Room(probably to reset names there).
