Again... when the only purchaser becomes the central bank, then you're effectively printing money. Since no one is bearing the cost of actually buying the bonds, and there is no profit motive, then you're ultimately just printing the deficit every year. This is already quite high, and is compounded by the knowledge that outstanding liabilities of the nation basically dwarf the current debt.

If that is the plan, then hyper-inflation is not only on the table, it starts to become probable. I shouldn't have to explain why that's a problem. There isn't a free lunch here. Yes, inflating the debt away is an option... to a point, but there are still hard limits on what the market will bear.