Long ago (2011) I mentioned a modular lighting system, including splitting the taillamp into reflector and emitting part the main lighting page and theoretical sections on headlamps and taillamps) and on 23-2-2013 I saw a new taillamp on a bike that's probably OEM-only where B&M do exactly this. Here are some pictures.
Click on the thumbnail images for a big image (1600x1200):
