I've got dynamo lighting on mine. I don't rate the Brompton wiring loom for anything other than convenience of fitting; you can do a better-looking job with Schmdt coax.
Additionally, I have Moon Comet be-seen lights as a backup (I like to run two rear lights, and I'm wary of the front light's visibility under luggage in urban traffic). The saddle rail mount means the seatpost can be fully inserted without touching the light. The front light can be mounted to the top of my S-type stem with the light in the vertical position, such that the light nestles between the spokes of the front wheel when folded (it often gets knocked out of sideways alignment slightly, but stays firmly attached). Not sure if that works with the other stems.
If you've got a rear rack, it's a complete no-brainer to fit a rear light to that in the intended manner. The Brompton lights aren't bad, and make an effort not to be occluded by the easy wheels. Otherwise mounting at the saddle might be more desirable, or a good place for an auxiliary.