100-ft high border made with reinforced concrete with sharpshooters at guard towers every mile. Time for Mexico to stew in their own juices.
You won't get any arguments from me. In the last century, there were all sorts of 'public works' projects done on a massive scale, such as building dams and such. When one compares the cost and benefits of those projects versus the benefits of what you suggest, it seems that a border fence would be a bargain. The big difference is that in the case of the dams there weren't Leftist politicians standing in front of the construction workers yelling "Racism!" as they are for the border fence.
Unfortunately, Mexico's problems have a way of becoming our problems. That is especially true when those problems result from the demand for illegal drugs in the United States.
Land mines every foot would be cheaper
If somewhat messier....