I have a bracket I got From Foldabikes, in Cal, it is a clamp on to then fit a braze on FD.
Steve Parry in UK has similar.
I liked the MD crank better.. $C and i'll sell the FD; Bracket and Thumbshifter to go on the bars.
unless people have tried it and failed and so not bothered to report on it!
or just did't report it, conveniently, Here.
one thing I see, [mechanic-think] adding it under the fixed cup moves the chain line off, alignment.
then you have to correct for that.,
presumably the double crank and new BB that you buy you will sort that out.
Dive in and then, make the report.. Tom.
BTW, no 12t for the AW3/BSR,only the no IGH 1~2 cog;.. or 6 speed BWR hubs.
BTW, Todd , partner in the PDX Brompton dealership, toured with just a change of crank
to 36,44t on his 6 speed , heel works to down shift, up shift done, stopped,
with fingers, when needed.