Not sure if I mentioned this before. Old timers disease?
I bought a pair of second hand Bromptons recently, which were already equipped with Shimano dynamos and B&M Lyt headlamps and Spaninga tail lamps. The Spaningas have a stand light function, but the Lyts don't. The Lyt also has one of the worst spreads I've ever seen in ANY light, and riding down a quiet, poorly lit backstreet gives you a rectangular hot spot about the size of an A3 or A2 page, which dazzles your eyes and prevents you from seeing anything outside this beam. I don't know why Brompton have chosen this arrangement (other than the Lyt is appropriately tiny), as the light is already so close to the ground that you really need the widest field you can get.
The Shimano and lights add approx. 440g to the weight of the bike, which is substantial with a Brompton. (These bikes also have titanium sub frames and forks, which is a hideously expensive way to save about 700g!)
Anyway, I'm not at all happy with the Lyt, so looking at my options. I could upgrade the headlight to an Eyc or a Luxos B, and the taillight to a Toplight Line Plus BrakeTec (my favourite)., and live with the Shimano. I could also swap out the Shimano hub for an SP, which is lighter and better quality.
Prior to reading this thread, I hadn't considered battery lights, but that is now a serious option, and the lightest, although perhaps not the cheapest.