Realistically though, the better way to address the problem is to progressively tax capital, no matter the income. A top bracket of 5% of capital gone per year will pretty much solve all but the most efficient of billionaire problems. And progressively tax inheritance in a similar way too.
I don't think it's a good idea, because of the second order effects. Assuming this tax can't be evaded (which, to be fair, is a pretty big assumption), high net worth individuals will be paying >100% tax rate. This means they will have to quickly sell the stock they own to afford the tax. And who will be able to buy it from them? This guarantees a complete, permanent crash of the stock market.
And this is just one of the problems. What about high-capital-low-margins businesses like retail stores and, especially, farmers?
Also, assessing the net worth of a person is incredibly hard. How much is a private company worth? One might think it's easy because Forbes does that, but they're mostly pulling the numbers out of thin air.
Realistically though, the better way to address the problem is to progressively tax capital, no matter the income. A top bracket of 5% of capital gone per year will pretty much solve all but the most efficient of billionaire problems. And progressively tax inheritance in a similar way too.