Perhaps a smarter idea for Ecuador is to take all of the USD they're circulating and convert it into an existing and proven cryptocurrency

Not sure how that would be smarter. They can spend these USDs (obtained via exchange into their EcuNewVirtualFiat) to pay back their USD debt, or to buy BTC or Dogecoin. Now, which one is immediately smarter?

"No fiat lives forever", true, but most well-managed fiat lives long enough for the former to be a feasible and indeed smart move.