I think the standard triangle is what, 110mm? I don't think 25mm wider would affect folding, as the rear triangle does not pass the top tube, only under, and 12.5mm per side should not be too much problem for the folded parts on the drive side.

I met someone with a Brompton with a Schlumpf drive, but I'd still like the simplicity of a double crank. 1X systems are nice, no duplicate gears, but difficult packaging on a 406 wheel, much less a 349, the rear derailleur is gonna drag on the ground. Plus I hate that the cassettes are riveted together for lateral stiffness on the big cogs, that makes cleaning a real pain.