>> With a graduated flat tax based on income groupings, each pays his own share.

That's how our current system started out and gradually the loopholes and deductions were added.
I agree that it would be a good idea.
Before you could put the tax accountants out of business though, you'd have to do something about the state and local codes. Many of them are almost impossible to understand.
Some of my colleagues maintain payroll systems and they spend a lot more time on state and local taxes than on federal.