>If a bank gets $1 million worth of new deposits, they get to issue... $0 more loans.

Then it doesn't make sense for a classical deposit-lending bank to pay interest on those new deposits. They can't generate revenue from the new deposits since they cannot touch them to perform lending , and they are now a liability because they must perform banking services to the depositor, regulatory compliance, and insure against the risk something accidently happens to the money. Under your scheme maybe they could go park it at the fed and get interest that way but even that is technically a loan; they are giving up the notional money in exchange for interest in hopes they can collect it at a later time.