I think the OP’s proposal is great but impossible to implement right away. Some steps have to be taken towards that direction though. First, eliminate borrowing using their stocks as collateral, thus avoiding capital gains tax. That would immediately reduce the number of new mega yachts.

But the biggest boon for society would be progressive taxes on inheritance. It wouldn’t be government’s problem to figure out how it would work. It would be on inheritor to figure out how to pay the taxes on their newly inherited wealth.