From your edge-case comment, it sounds like you'd prefer that losses from business income not roll over, rather than making rollovers accessible to individuals. I was approaching it the other way - trying to see if there was a reasonable way to credit individuals with a "P&L" view of their finances that could cross multiple years.

As you indicated above, so much of our personal expenses are "discretionary" in the sense that we could increase or lower them by choice. That's exactly the difference between business investment spending (required to produce the revenue that's taxed) vs. personal income/spending, which is based strongly on preferences. Hard to justify taxing frugal individuals more than lavish spenders just because they save a larger percentage of their income...