I live where its quite hilly, so I bought a different crankset, made for Bromptons,
by Schlumpf innovations, a Swiss manufacturing biz.

it is a planetary 2 speed , made so it uses the 3 speed twice,
shifting into low range on the crank and high gear in the hub,
and thats the next lowest ratio.

works well .. Mountain drive, for Brommys it's a 54t, 130 bcd.
[planetary low is an equivalent to a 21.6t chainring]
I have a SRAM made 15t cog on my AW3, so the direct middle gear is a 58",
you can fit a 13t or 14t on, to raise the range.

By both being planetary gears the shifting is quick on each,
tap the heel button in the center of the crank,
and flick the trigger shifter on the handlebar.