The Border Wall is already up across 700 miles of the border and is part of an extremely effective SYSTEM that has reduced crossings in ONE?
Why not continue what works that astonishingly well?
As to the myth that most fly in and overstay, you really need to study how those figures were conjured into existence.
Here is what the CBP has been doing since the early 90's along the border...
NICE FOLKS: The CA section of the Wall is built next to a railroad track and an interstate highway. But, then, it's only 60 miles of the 700 miles completed and proven effective. So, I'm not entirely sure why that even matters. The rest of what's needed has been figured in to the budgets proposed.
The video makes clear mention that existing sections have all-weather roads and all necessary improvements. And that they all work like a charm.