It's already a tried system in Baja California: import the LED/LCD panels from China, assemble in Mex, export to US.
The issue being that Mexico for a country with massive coastlines only has a handful of good deep water ports, especially on the west coast with Lazaro Cardenas, the busiest port in all of Mexico [1], only takes as much tonnage as Port of St. Louis, the 21st US busiest port [2].
[1] https://en.wikipedia.org/wiki/List_of_seaports_in_Mexico
[2] https://en.wikipedia.org/wiki/List_of_ports_in_the_United_St...
I suspect building 3x or even 9x standard width trains would be easier.
There are many advantages to water transport over rail, where water transport is possible. water transport is vastly more efficient. The gauge isn't the reason for that, though; the efficiency is in the same order of magnitude regardless of gauge. Water transport is about one order of magnitude more efficient per mile, iirc. Trains are usually faster and more direct, which is their niche.