Ooh...good point with the lights being too low. As for hacking standard lights to fit the pillar, a pack of sugru will address that problem seamlessley.
If you don't know what sugru is, look it up. The handiest stuff on the planet!
Not knowing much about bike gearing in general, the Brompton brochure says the standard 6 speed gear range is 33.1"-100". The -12% version is 29.1"-88".
Then the 3 speed is 47.9"-84.9". The -12% version is 42.1"-74.7".
So based on numbers alone, I can't tell if the normal 6 speed or the -12% would be better for me. I don't plan to go super fast on the flats (got a 3.5 yr old just learning to bike, so it will be a while to really be able to go fast). And we live in a relatively hilly area, but the local bike trails are relatively flat, LOL.