Okay, I've been messing around with the renderers quite a bit, and here's my big wish: For Superfly and Firefly, there should be a way to plug global effects processes at the back end of the process. In other words, let all the individual objects have their individual materials as they exist now, but intercept the process for ALL of them to apply procedures and textures across the whole render. And, of course, there should be a tick-box for each individual element or group of elements to exempt it from the global process. It seems to me that Preview mode allows this- the toon display mode, for instance, but the display modes don't allow much fine control or any insertion of user procedures.