It would also be laughably easy to solved the billionaire income tax problem.
If the total amount of loans you've taken out using investment vehicles as collateral is over a certain variable, it's taxed as both income and a realized gain.
Something like, 100x the take home pay of the bottom 20% of workers, which is about $1.6m. Maybe have an exclusion if the loan is for a primary residence if you have no other real-estate holdings.
This also has the added benefit of them needing to pay people more to get cheaper loans.