I couldn't agree more. I think it could be overcome with extra pre-bate money based on a calculation.
I know that the Roth is great for middle income wage earners from my own experience. As I've started my own business and my company income has risen, I have found that the 401K or SEP route to be most advantageous due to avoiding employment taxes on what I contribute. That is not available to most people, the majority of Americans. So although it wouldn't affect me that much right now, I think that it would be a huge issue for most people; this is the biggest hurdle for being fully on board with the fair tax. Not out of selfish reasons but what is best for the country as a whole.
It might not be double taxation but is is definitely twice taxation.