Earlier quoted context omitted.
Why couldn't you use short-term fed paper? Even a 0.5% yearly yield would be more than enough.
But why would you use short-term fed paper to make money with your stake, when you could just plain buy short-term fed paper, without the risk of people "redeeming" it from you? Backing a currency isn't about taking deposits from people. You can't back with deposits because your liabilities = assets then. You have to put your own stuff up, but then all you are doing is running the risk that people will redeem it away…
And if people redeem from you, just add a clause where if the liquidity pool is gone you have to wait X days before getting it redeemed.