And you can't actually lengthen payments for everything - some businesses and people with important resources will simply demand an up-front payment. Which will worsen the crunch for those that are stuck in the middle - some businesses will have to pay upfront, but get paid 3 months later. And no, banks won't want to lend to these businesses and if they can't determine whether you're one of those businesses or not, they will tighten credit on most businesses. Not to do so puts their own creditworthiness at risk.
This is all assuming you have perfect execution too - in reality, there will literally be millions of lawsuits since no one will be able to actually define what you're saying precisely enough to make the implied alterations to existing contracts unambiguous. It's also important to understand that most payments aren't interest payments - some of these cover actual costs.
Edit: consider what every company in the world will do in response to do this - they will review every contract they have to see if there's an angle that will help them optimize for this situation, and what kinds of addendum that they can force on others would put them in a more advantageous situation. No one will just sit and work according the spirit of the new rule, any ambiguities and angles will be exploited and lots of businesses and people will go end up on the wrong end of this.