The only thing I have against using crypto as currency, is that it's finite. Which means that with every coin that falls out of existence, the rest of them gain in value. That, and the electricity/hard drive wastes are the only things that have bugged me about crypto being used as currency.
There's also the fact that currencies don't have intrinsic value. They can't. It's why the US left the gold standard and switched to our lovely debt model. Historically, tribes have used feathers, gold, rocks, seashells, etc. None of this had intrinsic value. Until Gold became useful in electronics -- and some other fields. Then it gained intrinsic value, and we had to get rid of it. Bitcoin has intrinsic value.
The reason you don't use intrinsic value for currency is, intrinsic value drives the market. Things are worth what they can be used for. And use goes up and down. Hence, why Bitcoin is never stable. It's used for more than currency. The intrinsic factor is playing with Bitcoin's market. And it's hard to buy a loaf of bread when you need 2 coins today, and 12 tomorrow.
It'd be cool to see crypto as the currency of a nation, but I think they need to make their own. Something separate from the market, whose value is based solely on social construction. Legal fiction would be a better term though.
But those are my 3 problems:
The currency is finite.
It uses a vast amount of resources to produce.
It's intrinsically valuable.
Fix those and any country should be able to use crypo for its primary source of money.