First, it essentially already is the banks' problem legally. This does not stop a bank from defrauding the customer into giving the bank a loan for months while performing hundreds of hours of paralegal work, but in most cases the bank will eventually be on the hook. So we're not talking about any new risk, but rather for banks to stop giving people the runaround pretending they aren't directly responsible.

Checks would be completely unaffected, as they're already reversible like any other ACH transaction.

If there is any affect it would be on cash withdrawals and wire transfers seeing increased authentication requirements (places where the transaction "hardness" of money increases). But that's precisely what we want to happen! I do personally withdraw thousands of dollars in cash at a time. But if say I had to use my ATM card + PIN instead of merely writing my 9-digit account number on a paper withdrawal slip, I would certainly understand.