Would running a wider rim help? I have the same issue on one of my bikes but it really isn't a big deal since I only use the bike for pleasure but I do have a set of 700x36c tires on a very narrow rim with a very pronounced light bulb profile. I have thought that if I were to use a wider rim, the light bulb profile would be much less pronounced and then I could use the thin cup washers on the brake pad post on the wheel side which would allow the pads to be further out. Then I thought that if I released the brake cable, I would have enough clearance. I haven't done this because its not really important to me but I think it might help.