Although it will probably be lampooned as Trump-esque, I think another solution would be to negotiate some sort of deal with Mexico where Mexican nationals can live here, not be citizens, and the Mexican government has to pay us back for their healthcare, education, and any welfare they take. Healthcare is the main issue. As I've said many times before, open borders make universal healthcare impossible. Mexican immigration will stretch even just Obamacare to its limits, as most Mexican immigrants, if made legal, qualify for Medicaid.
sort of agree with this tbh. i think you would have to have both countries agree to land swaps and/or have that 'zone' extend into part of the present u.s. for it to work though