Just like now your stock value would not be taxed while it is invested. But now it would be taxed if you use it as collateral for anything. If you don't want to pay capital gains by selling the underlying stock then you can just get a bigger loan and pay the taxes out of that.
There, now you don't have to liquidate but the taxpayers benefit too when the wealth is "used" by the owner.
I think the sensible option is making death a taxable event, rather than borrowing (with perhaps exceptions for the family farm, but not for the family billion dollar business).
And the second best solution is eliminating the step-up basis, which without deemed disposition at death is just a free gift of capital gains tax rebates to heirs of the most wealthy.
1. No one really borrows against the value of their (paid off) car. 2. Property taxes already, generally, are against the assessed value of the home, so it's already happening for that case. There are some minimal exceptions, like CA Prop 13, of course, but generally speaking, if I want to take out a second mortgage or something, my home's value is already appropriately "stepped up."
But I now assume the tax would be on the assessed change value of the asset, for which a new car or home would be 0, so no tax.