Perot and Forbes both tried to get some flat tax stuff passed and nobody went for it. You'll do better trying to pitch an automobile that runs on water to the oil companies.
Even if there was a flat-tax, the wealthy will figure some way out of paying their fair share. Either by putting property, stock, bank accounts, and other stuff in a different name or a different country, or by getting lawyers and accountants to find ways around it and cheat on taxes and hope they don't get caught.
Oh no, we cannot have a tax system that makes the rich pay more, but we are stuck with a tax system that makes the middle-class and poor pay more and the rich get away with murder? I am all for a fair tax system, the current system is unfair! We need a reform!