Unless their spouse is still alive. In the US, assets' cost bases are reset when a spouse dies. That is the main way that rich people avoid capital gains taxes. I'd much prefer simply stopping that cost basis reset instead of implementing a wealth tax.
Neither of these would really work against the people you actually want it to work against.
If you don't have a basis reset then they just do a transaction that has the same effect, e.g. create a new corporation owned by the recipient and then have it repeatedly enter into slightly favorable transactions with the one owned by the donor until the new one has all the assets, or any of a hundred other things.
If you try to do a wealth tax then their assets end up in another country under whatever arrangement is necessary to give them de facto control but not formal ownership.
The best way to solve the "buy, borrow, die" thing is actually a consumption tax because then borrowing money in order to spend it doesn't avoid the tax.
Of course people will try to cheat taxes, but they'll try to cheat any form of tax: income, capital gains, inheritance taxes, etc. People are good to try and evade taxes regardless of the tax mechanism.
Consumption taxes are regressive: a sales tax is a flat tax that taxes a billion on their $10 latte the same as a poor person. Consumption also doesn't scale linearly with wealth: most billionaires don't consume 1000x as much as a millionaire.
You croak, your heirs become the beneficiaries of the trust. Rinse, repeat.
Re: estate taxes - almost no ultra rich pays them, even without surviving wife. According tom Garry Cohn (former big kahuna at Goldman Sachd and former treasury something or other in the first Trump admin) only morons pay estate taxes : https://www.cnbc.com/2017/08/29/only-morons-pay-the-estate-t...
