>First, you get a horrible incentive to not repay debts
Isn't that what credit ratings are for? You'd be able to do this exactly once for any meaningful amount of money, and then your financial life would be otherwise over.
You can walk away from hundreds of thousands of dollars in mortgage debt and still have a 700 credit score, all of your credit cards, and the ability to still get credit.
Defaulting on debt doesn't mean your financial life is over by any means.
Isn't that what credit ratings are for? You'd be able to do this exactly once for any meaningful amount of money, and then your financial life would be otherwise over.