one big issue is everyone goes “you can’t tax stocks!” and then billionaires take a loan against the stocks with the unrealized gains as collateral. So we’d need to start classifying a loan as a realized gain of the collateral against this, with an exception for mortgages on primary domiciles, maybe also a “first million dollars are exempt,” calculated on the full debt of the borrower, not per loan. I can’t imagine anyone taking out more than $1M in debt against a properly they don’t live in is not the rich we need to be taxing.