Sure, but I think this would actually help a lot of working or middle class folks more than it would help the rich. If you were rich, it wouldn't really matter how much you "spread income" because your typical standard of living would exceed the higher tax brackets anyway. So this would actually be a benefit to working-class or middle-class folks with inconsistent and bursty income, which is a good outcome.

If you were worried about say, frugal people with large amounts of generational wealth, you can also pair this with a big fat estate tax.