Cross-chain mixing works for some purposes, but Putin/Kirchner/Obama's tax thugs and lickspittle corporatists will demand to know the origin of your coins. Which is effectively a whitelisting approach putting the burden of proof on the user to prove their innocence against the presumption of guilt.
Right, what do you do when you buy something with such spent Bitcoins or Moneroj, when they come back and say, "We know you bought such and such with these, because it was shipped to your address. We now need a verifiable record of when and where you bought them, because you now potentially owe capital gains taxes on them."
I would advise everybody to just follow the rule of the law in your particular jurisdiction. :-)
