But that's not what Trump has been saying.
Actually he did say it a couple of times that I heard at various rallies. But most of the time he did give the impression of an edge to edge wall.
Also, there is already a wall along part of the Mexico- California border and the Texas-Mexico border. If he tarts building a wall and implements the facet of his plan there may be enough self deportation that he can claim victory and stop.
A last point, if I were a rancher along the US/Mexico border and had armies of illegals and their armed snake heads or drug cartel types crossing through my property and some of them do, I might donate the land.
I still think introducing piranha into the Rio Grand would work.