A currency as a "negotiable instrument" only works because:
A. Everyone agrees that it does,
B. Because the controller of the currency has value with which to back the currency
B is less important these days with Fiat currency, but A is essential.
Unless you're a country's central bank, nothing you make as a "negotiable instrument" is going to be recognised as such - and even if it was, if you've no valuabke resource with which to back it up, it's worthless, so nobody would want it.
I feel sorry for these people because I do get the sentiment behind it. They feel like they're being screwed over and want a way to fight back - but if it were this easy, everybody would be doing it.
Essentially, they're writing $1,000,000 on a piece of paper and declaring it to be worth the full amount of the debt. The bank issuing this "coupon" being themselves, who can totally back this coupon's worth.
Kinda like if tried to pay your bills with monopoly money.