So many people just reflexively say, don't bother taxing corporations--individuals are the ones ultimately paying the taxes anyway. So what's the difference if individuals are not made to pay income taxes? They'd be ultimately paying anyway, right? And you've increased the simplicity of life and freedom of the vast majority of people who aren't business owners. 401ks and Roths? Irrelevant. 529's? Just save and invest in your own. No tax shelters needed. The IRS can shrink as it focuses on a smaller population and more limited tax codes.
If you've only considered one side without giving fair consideration of the opposite, you've only done half the job. Honestly, this idea just popped into my head, but I think that it would prove to be and invaluable thought experiment no matter the ultimate conclusion reached. We keep using the same assumptions, as if they are written in stone, but they aren't, and all it does is lead us down the same old paths.