When Unrealized Capital Gains becomes large enough, and the owners of this stocks, bonds, commodity has sufficient connects, then they are able to "liquidize" this Unrealized Capital Gains through loans by using the Unrealized Capital Gain as collateral for their loans. The Richer they are, the closer to parity they are able to "liquidize" their Unrealized Capital Gains.
Therefore, Unrealized Capital Gains should be tax only if it crosses a threshold, but that threshold is too vague for now. Another way to counter Unrealized Capital Gains is to treat Loans as Income and loan payment as expense (negative income) to modify for the intermittent effect of loans. However, this will create a new vocabulary of some sort of "Bartering" without formally classify as "Barter" to bypass taxes.