This article is paywalled for me. From what I can make of the excerpt you included, I made a similar proposal back in this post. Instead of a flat 10% tax on the loan, I would just use the existing income tax percentages already in place, so 37% for income over $523,600 in 2021-2022.
Simultaneously, I would raise capital gains tax rates to match income tax rates, if the net worth of assets sold that year exceeds a certain amount. Combined, these two initiatives should close all the major loopholes I can think of at the moment, but I’m sure they’d come up with more ingenious ones. It’s still a good start, though.