It's a terrible idea to give all the power to idealists (even granting this is possible). Corrupt cynics can be bargained with. The damage idealists can do is unbounded.
Hey, my answer is actually to eliminate the position and put no one in power. I don't trust all idealists myself, though I'm not convinced corruption is better. But the OP was pinning for the rose-tinted days of yore when great politicians ran for office to do good and not to make money, so I suggested a scheme designed to encourage exactly that.