Reasonable, but if there is to be a DMZ it rightly belongs on the Mexican side of the border.
Should be installed “well south of the river”. The Rio Grande originates deep inside the U.S. So as far as I’m concerned, the entire length belongs to the U.S. If meh-eek-0 don’t like, too bad.
You never put your defenses right on the border. You should place them strategically.
That’s why the Maginot and Siegfried lines worked at the beginning of World War II. At places the Siegfried was 5 or 10 miles back from the French border. The French invasion of Germany in 1939 quickly gained the territory in the border area to a depth of several miles, but stalled out when they got to the Siegfried despite an overwhelmingly superior force. The campaign devolved into a back and forth in the area in front of the Siegfried over the next month or so, but with no real threat to the area defended by the Siegfried.