Sorry, but that's what El Salvador did - they called it Legal Tender, so they created a law that said if you sell bitcoins, you dont have to pay capital gains tax on it. You dont need bitcoin to have intrinsic value, and it dont matter if its being manipulated like fiat. It just means what it says, you dont pay capital gains tax on selling bitcoin.
I'm sorry if you dont like it, but it literally is cheaper for them to send to El Salvador bitcoins and get it converted to USD than for them to send USD. You want to pay $20 to transfer your money, or you want to pay $1 to transfer? $19 is a lot for them.