Hold a national referendum on the tax code and proposed changes through a series of conventions in each state that any citizen can attend, participate in, and where the proposals are voted on by the people in attendance.
The goal is a fair and just system that comes from the people rather than special interest groups.
This can be achieved by the process of elimination -- removing the proposals with the least votes: compile the top 10 from each state, and then vote nation-wide, take the top 10 and vote again, then the top 5 and vote again, and then taking the top 2 and vote for the final plan. Let everyone have two votes: one for, and one against.
Future changes to the tax code could then be approved by the people during national elections.