The major problem is converting between real crypto and CBDCs (and other government-controlled electronic money) at the same time preserving the anonymity of the real crypto wallets and the anonymity of the crypto transactions. I have been thinking about it and it seems that there are various ways to organize this conversion between real crypto and CBDCs as long as the users are allowed to transfer freely CBDCs (or other government-controlled money) from one government-controlled wallet to another without significant cost, i.e. minimal or no government taxes for such transfers. I think that if this problem is solved, then the remaining problems will be solved too.