For instance Congress could legally declare that a one dollar bill is legally exchangeable for 1/1000th of an ounce of gold or 1/25th ounce of silver at any Federally chartered bank.
Congress could legally follow your suggestion. Just because it's legal, doesn't make it a good idea.
So you think that the Founding Fathers restrictions against Congress issuing paper money was a bad idea then or do you think that following the Constitution now is a bad idea?
Which is it?