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.