Nice idea, but I think this overlooks the fact that (ideally) taxation needs to be progressive.
If say everything is taxed at a flat 20%, then someone on the breadline pays the same percentage tax as a billionaire.
Quite ironic, bitcoin doesn't care about the sum involved but the amount of space used, so if we would impose taxes after the blockchain model they will be neither a fixed percentage nor a progressive percentage but a fixed sum for everybody. So no 1% of 1000 or 20% of 2000000 but rather 100 for everyone. Remember, Bitcoin is the total opposite of socialism or socialism measures. And just to hammer that idea once more, Bitcoin is the perfect tool for rich people to avoid taxation at all, so in your ideal world there would be no place for it.
However, take note that there are still bitcoin friendly countries that made it to non taxable like Portugal and France.
The solution? Follow government laws for less conflicts.
In France, crypto trades are no taxable, or transfers between addresses but when you exchange crypto to fiat you're taxed, and if you try to purchase something directly with crypto you're also taxed with VAT just as with fiat.