Don't misunderstand me - I'm all in favor of giving veto power to as many countries as possible, but I can't see why Brasil would be more deserving of it than Israel.
Brasil is a democracy and the fact that at this term they have elected left wing government does not mean much. Would you propose to remove USA from the UN Security Council when liberal Democracts get into power?
The main reason why Brasil would be a proper choice is that it is the largest Latin American country and it would be fair if their continent were represented.
Nigeria could qualify for similiar reason. So I would add India - the second most populous country in the world and the largest, most free democracy (although not rich), Brasil and Nigeria as permanent memebers without veto power.