Would this not require a constitutional amendment? The XVIth only allows tax on income. Wealth is not mentioned.
Yes, a wealth tax would be an unapportioned direct tax that is prohibited by Article I, Section 9 of the Constitution. A Freeper who was proposing a wealth tax a few months ago claimed that the 16th Amendment repealed that section, but the Supreme Court has held to the contrary multiple times.
Warren is a smart enough lawyer that she is probably aware of all this, so I wonder how she expects to get around the constitutional problem.