I think the arguments given by IMF are so lame that an undergraduate Corporate Finance Student can give solutions to them:
The two IMF officials alleged that countries adopting cryptocurrencies as national currencies or “granting cryptoassets legal tender status” risked domestic prices becoming highly unstable, also emphasizing assets being used contrary to Anti-Money Laundering and combating the financing of terrorism measures in addition to having issues surrounding macroeconomic stability and the environment.
So true terrorism was actually founded after 2009, it didn't even exist before that, terrorists use to work for free before that. I don't see paper notes being banned so far. Also KYC is a very simple procedure to ensure that illicit activities can be stopped to great extent. At max you can say is that citizens can only make payments from KYC wallets to other's KYC wallets. If this happens the money trail is unbeatable, no other technology can provide a better trail for sure.
“If goods and services were priced in both a real currency and a cryptoasset, households and businesses would spend significant time and resources choosing which money to hold as opposed to engaging in productive activities,” said Adrian and Weeks-Brown. “Government revenues would be exposed to exchange rate risk if taxes were quoted in advance in a cryptoasset while expenditures remained mostly in the local currency, or vice versa.”
Government can easily eliminate exchange rate risk either by maintaining adequate forward or options contracts in the future markets until the expenditures become in crypto assets, which they will soon become. In fact the government should devise a policy to ensure most of the expenses like salaries are made in crypto assets that are received in taxes. A simple survey could be sought from the people to ask about their choice of mode of payment of tax. Government can then plan its budget accordingly.
They also claimed that monetary policy, in general, “would lose bite,” implying widespread crypto adoption lessens the credibility of any country adopting an asset like BTC or another token, and pointing to the “massive fluctuations in cryptoasset prices.” The price of Bitcoin has already moved between roughly $65,000 and $30,000 this year and reached more than $40,000 on Monday before dipping to the $37,000s.
That's not even an excuse, compare it to Zimbabwe and Venezuela, why isn't IMF more concerned about them first? Hyperinflation is at it's peak here.
https://peoplesdispatch.org/2020/03/19/imf-refuses-aid-to-venezuela-in-the-midst-of-the-coronavirus-crisis/