If you had a tax like this, have it last for a period until some semblance of balance is restored between the different wealth quintiles.
The goal isn't to produce equality. It's to reduce the gross inequality which low tax rates on the extremely wealthy have produced.
A difficulty I can see with a wealth tax is that it would be hard to construct proper legislation from a practical perspective because: (i) some sorts of wealth aren't liquid, (ii) some sorts of wealth are not in the US and so US jurisdiction may not be operative (eg the IRS cannot seize control of commercial property in Germany it might claim from a US billionaire whose ownership exists via a Panamanian trust (think endless litigation)) and (iii) some sorts of wealth are hard to value.
Generally-speaking, this is why governments tax income, instead.
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