If you liked Paine's idea about legal tender, you'll love his idea for a welfare state. That way you can enjoy the freedom of giving your gold and silver to your less fortunate countrymen and not have to worry about sticking them with worthless paper.
You are still missing the point. If Congress made Pieces of Eight “legal tender” until 1857, it was still exercising a power not granted by the Constitution, and if it barred their use as legal tender, it was also exercising a power not granted. I am simply advocating a straightforward interpretation of the Constitution that would bar Congress from exercising the power to say what must (or must not) be used as legal tender.
BTW, I am wondering if you have a citation to any statute making the Spanish Dollar legal tender, as opposed to the 1857 statute outlawing it, which I did find (and learned something, thanks). There is supposed to be a definitive work on the subject, The Monetary Powers and Disabilities of the United States Constitution, by Edwin Vieira Jr., which collects this sort of material.
As for Thomas Paine, nobody is perfect. I have never read his Agrarian Justice tract, so I am not too familiar with how far he may have strayed. But I remain mystified by your evident hostility toward gold and silver.