First of all, who do you think the "rich" are?
Second of all, it would be the fairest system and it will be practically impossible to cheat. Obviously the rate must be low, like 20%..
I was refering to those with higher income (relatively) who fall within a higher tax bracket. I agree it will be hard to cheat with a flat rate no deduction system, but higher income earners like you would be worse off.