I feel like Tony Blair would have to be insane to take a job as special envoy for the Israel-Palestine conflict. Obviously, bringing about a peace agreement there would assure Blair's legacy, but the odds are not only dim, but would to a large extent be left hostage to George W. Bush. Unless Blair is completely addled he surely must have learned the lesson that putting himself in the middle of risky, speculative endeavors involving Bush in a crucial role isn't a good idea.
What Blair needs to do is find himself a nice, fairly uncontroversial issue to work on. HIV/AIDS is always a solid choice, but I think Bill Clinton's cornered that market. Access to safe drinking water would probably be a good idea.