Good idea, but how would you propose to combine the outputs of several light pipes into a single source? I don't think it can be done because it would violate the second law of thermodynamics, also know as entropy. In other words, light exiting multiple light pipes is basically random (chaotic) in nature (direction polarity) and is spread over a relatively larger space (i.e. lower energy density). To convert those outputs to a single source (i.e. less chaos, higher energy density) without losing some energy in the process would go against the entropy principle. For the same reason you cannot focus the light emitted by a give surface area (think LED die), onto a smaller surface without losing some of the light in the process, no matter what kind of optics you used.
The situation would of course be different if you were talking about laser light, which is not random. You COULD combine two or more laser beams into a single beam without any loss, e.g. with beam splitters.
Also I believe that LED-to-light-pipe and LED-to-fiber-optic optocouplers are far from being 100% efficient, so there would be plenty of losses just getting the LED light to go into the light pipe.