We are never going to get a system that is perfect. We have to experiment. We really have to depend on the integrity of public office holders to make difficult decisions like this.
My experience of looking at political scandals federally and provincially is that the people we have to worry about are those whose finances are close to the line. They might be tempted to do something unethical to make sure that they have a nest egg when they retire. If someone is very, very well off, they're much less likely to be tempted to benefit themselves, because they're already pretty well off.
As I say, you raise legitimate questions, and they're something worth looking into more thoroughly.