Unfortunately, this and the fact that a few former U.S. and foreign soldiers are doing likewise, have been well known within law enforcement circles - especially the USBP - for quite some time.
You are right. Law enforcement has known this has been going on long since before I worked narcotics on the border in the 90's.
I think National Guard units should rotate in and out of the border states for summer duty. The rest of the year the Army should patrol it.
First we have to undo the treaty we signed with Mexico promising not to patrol our borders with troops. It scares them.