The only place to get more tax is to just seize the paper straight. And I think that’s a terrible idea.

That's not true, right now there's lots of incentive for the ultra wealthy to not sell their stocks, and instead use the buy/borrow/die strategy. This results in less tax revenue, allows them to capture gains, and can then pass down that wealth on a step-up basis that wipes out capital gains for the recipient.

Policies could be changed to incentivize selling assets without actually seizing them.