You could buy a 'universal' cable that had a brake terminus on one end and a shift terminus on the other end. Handy to carry as a spare on a long tour.
Please provide a link to this as I've never heard of it. The cable diameter is different, 1.6mm for brake and 1.1-1.2mm for shift. Explain how this would work. There are 'universal' brake cables that are mountain on one end and road on the other, and shift cables that are Campy on one end and Shimano/SRAM on the other...but a cable that doubles as both shift and brake? I doubt it.