Should work. In theory. Shifter cables aren't as thick as brake cables, so you'd either have to use shifter cables to the brakes or check to see if you could get a brake cable to work in the shifter--there may be interference issues with the head inside the shifter, and maybe the holes the cable runs through is too small diameter for brake cable. I think if you just take out the spring mechanism that works with the molded detentes in cheap Grip Shifters, you'd get what you are looking for. Since there would not be any kind of spring return in the shifter, you'd want to make sure your spring tension at the brakes is ramped all the way up and that you have brake housing runs with no tight radii or kinks. Real issue is going to be what kind of leverage you can get out of the shifters--if there's enough cable pull to make the brakes work.