I did. And I did not see any indication how Trump (or anyone else) thinks this "solution" will prevent 50 other ways for illegals to send money back to Mexico that do not involve wire transfers.
All your 50 ways are illegal, and involve dealing with criminals who will take at least as much as the 25% the banks would, and no real guarantees the people in Mexico will ever receive the money. Or are they going to set up these transnational money laundering networks out of the goodness of their hearts? Nope, people will just continue to use the banks and give up the 25%.
It is a little harder if illegals are not here, don't you think?