You’re kind of suggesting two different things there. Should loans on financial assets be banned, or should the amount able to be leveraged be limited?

Either would have massive unintended consequences. Mortgages on homes as well as secured car loans would have to be either discharged and re-applied or the terms redrawn. They could also be forgiven, but then every financial institution would go bust or the government would have to step in and shell out insane amounts of money. It would at least cause another GFC, if not a global depression, if done quickly.

I’m not discounting the idea necessarily, but it’s always important to consider the unintended consequences of a simple idea.