It's harder than it looks because T bonds come due on an ongoing basis, and even if borrowing stopped their regular sale must continue to pay due bonds and hold the debt at a steady level. But if you start to deliberately inflate the money supply by more than the usual few percent, you get less for the bonds, so the cost of servicing the debt goes up even as you're trying to hold it steady in nominal terms. Or something like that. There is a positive feedback involved that could be troublesome.