A HUGE amount of complexity in tax code, tax preparation, and tax audit is the characterization of earnings.
Pop quiz, if you are going to be bringing in $100M, do you want to pay 40% tax or 15% tax? Long term capital gains = 15%. So a lot of hoop jumping to turn things into capital gains, then long term capital gains. What a pain.
Just for simplicyt I wish they would say, for everyone making more than $150K/year (300K married) investment income is taxed as any other type of income.
Cut overall rates if needed if you want it revenue neutral.
The next step is to tax unrealized gains. I know, lots of hand wringing, but if you can defer gains until death (not too hard) you can come out golden in terms of family wealth (lots of like kind property exchanges etc).