The vote is for cooperation between executive branches, but that doesn't necessarily mean that the Regional Houses, Courts, or the National Senate would agree to cooperate with executives. In any case, there is a 4th President - the Outer Region, which consists of Alaska, Guam, Hawaii, Djibuti, and other small yet significant territories. I am of the mind that with a lack of raw land and people, the Outer Regions should get some sort of outsized advantage to compensate. A president's vote being equal to their peers is probably simple enough to do the trick.