Congress (NOT the President, and NOT the Department of the Treasury, Bureau of the Mint) has the exclusive power "to coin money, and regulate the value thereof".
It would be perfectly constitutional for Congress to authorize by statute a 1 ounce platinum coin with a face value of one trillion dollars.
Of course, they would thereby create a few problems. But it's not illegal, it's not unconstitutional, and it would increase the money supply by however many coins were minted, without raising the debt ceiling.
No doubt, and perhaps you would say Congress has been doing that— but it has not. The Federal Reserves is “minting” or “coining” our “money” in electronic blips and at their all knowing whims.
The coin could be composed of ANYTHING. But they wouldn’t do it out of anything for the fact there is no value in say a wooden nickel. So instead some genius thinks, platinum, and would have to establish a value for the quantity of metal in it. Since the metal is a traded commodity, the “coinage” would be suitably meaningless. This is overall a foolish exercise, just as returning to a “gold standard” would be, because once again all the gold in the world that has been refined would fit in a cube 60 meters on a side.
The answer is to control the size of government— top to bottom audit— stringent thorough and complete. And then walk through each section of it— cutting away the vast waste that our govt. is.