That's not an opposite notion, really. The opposite would be Mexican soldiers shooting down americans making a break for mexico. :-)
In any case, I am sure there would be a deterrent effect, but even with the military presence a lot of folks will try to take advantage of the holes. Enough of those folks being shot dead will be more than enough to turn the stomachs of all right-minded Americans.
There has to be a better way. We need to think of one, since illegal immigration is a huge problem.
People would be shocked to know the border is already very militarized on the Mexican side --- their army is there --- crawling all over the border. There isn't an illegal who won't tell you that --- many aren't sure what they're doing --- but they will stop people --- sometimes they're looking for Central Americans but they apparently are looking for drugs --- not necessarily to stop the flow of drugs into the USA but to protect one cartel from competitors.