If you are not locked into big wheels , Bike Friday .. My Pocket Llama Has Disc Brakes..
Its frame tube is low [20"] and easy to swing my feet over it , in mounting/dismounting..
Neither of those bikes you referred to have fittings for disc Brakes , But wheels with Drum brakes dont need special frame fittings
but are good braking in foul weather Or Fair.
My Studded tire bike has Drum brakes , built on an old MTB (way pre Disc)
European market, as AF-7 offers , is Koga's super metro Ladies.
http://www.koga.com/koga_uk/#6