Who needs BTC? Trump's plan won't work even without BTC. There are many businesses in the US trading with Mexican businesses, and then there are millions of Mexicans living in the US who carry a US passport. Remittances are only a very little part of the money flowing above the US/Mexican border, and you can't stop them without hurting everything.
Also, from a legal point of view, depriving an individual from the right to do what he wants with his money, will be difficult. Mexicans (hey, they're not all illegal) would easily find lawyers to protect their rights.
Not only that but, when you file a claim,
at a Federal or United States District Court,
against any man or woman who harms you,
be they government employees/officials or not,
and be you a "citizen" of the U.S. or not,
it is you against that man or woman.
If you do it without being the client of an attorney,
and don't use the attorney except as co-counsel,
(for directions on what paperwork to file),
the court is a court of record between you and the man or woman who harmed you.
The judge in a court of record is simply a magistrate,
one who keeps general order in the court, and,
who witnesses the proceeding as a witness.
He is not a judge unless you ask him to be.
The jury is the judge, if there is one.
If you have a strong case, the verdict of the jury can't be appealed.
A new case needs to be filed by anyone wanting to appeal.
What this all means is that anyone who feels he has been harmed by anyone else, be they a government official or not, can face that person in court. When "legals" or "illegals" wake up to this fact, Trump's plans will wither on the vine, along with those of the IRS or anyone else. Google and Yutube search on "Karl Lentz common law."