What do you think are the main problems of cryptocurrencies that stop them from becoming real money and real medium of exchange (volatility, etc.)?
It really depends upon what is your definition of real money. Bitcoin can surely be used as a medium of exchange. I tried an experiment last year. I bought commodity from one of my client who is good friend of mine and owner of e-commerce business. Then I reported this transaction as per Indian Accounting Standard 21 (Ind AS-21) which deals with 'The Effects of changes in Foreign Exchange Rates' and treated Bitcoin as foreign currency.
While filing his income tax return, I reported transaction as foreign exchange transaction and it was cleared by Income Tax Authority. Then we tried availing one of the government subsidy and submitted same Balance Sheet. To my surprise, even Central Government didn't object the presence of 'Exchange Loss' account in the financial statement and approved our subsidy application.