One reason for thinking mixte: the diminishing flexibility that comes with age. I can almost always swing my leg over the saddle, but sometimes I get hung up for a few seconds. I can imagine not being able to do get on and off a DF, at which time a step-through, low-cost, old, used bike in my size made with double-butted steel with the strength of 531/SL/SP/Champion/022/etc. would be very welcome.