It already did.
What already did?
The banks turning in their debt as "collateral" (soon to be monetized) must do so because they leveraged their actual capital 10 or 20 to 1 and are getting margin calls.
I don't think you understand what a margin call means. I'll add it to the list.
The banking system as a whole picked up the multiplier. It is an error to state that any one bank multiplies the money. I know what a margin call is and as you explain below, the T-Bills that the investment bank borrowed can meet the margin calls. Now the Fed has gone further, Bear Stearns has an undisclosed credit line of T-Bills from the Fed through JPM for more than just margin calls. Will they pay those all back? Sure. Maybe. Maybe not. It is certainly possible they will default on some of it.