Figure out some baseline income, don't tax that at all for anyone, and then have a flat tax for everything above that. The poor pay no tax, or virtually no tax; the rich pay a lot, but at a fair rate, and there is still incentive to increase your income, unless you want to stay at the poverty level. Simple, fair, effective, but would put too many lawyers out of work, so it'll never happen.
The problem with any scaled tax is that there is a point on the margin you benefit from making less. Lets say "the line" is $20,000. Above that, you get a 15% tax rate.
What are you going to do when you realize you're going to breach the 20,000 line by a hundred bucks? Thats a $3,000 tax liability you didn't plan for that you're about to incur. Have fun paying that unexpected bill on a $20,001 yearly wage.
Additionally, removing the deduction system would absolutely obliterate charitable giving. There are a whole lot of rich people who put billions into the charity system every year because they don't want their hard earned dollar going to "the man".
Every time we get into this discussion someone asks "Could it be any worse than our current system?" I've determined I feel a bit like Churchill:
Our system is the worst taxation scheme except all the others that have been tried.
I certainly believe that we are taxed too much. I believe the government uses
my/our money for mostly the wrong things. I also think the system in place although not perfect, is effective. If you want a lower tax rate, we should spend less as a government and extend the cut equally across the board. Lower tax rates will always encourage greater prosperity.