Just a quick thought here, and of course partially tongue in cheek…
But if the southern border is truly an emergency, requiring executive usurpation of the powers of congress…
then why not send in the entire military, shut down all traffic, shutter the border crossings, and so on?
Why, if this is an existential crisis, a national emergency… commit to spending 5 billion dollars to build far (far, far, far!!) less than 25% of the total wall — something that will take many years to complete even if we start tomorrow with a full-scale national effort.
Emergencies are not dealt with using long-term solutions. Emergencies are met with immediate action.
There is no logic to calling anything about a wall an “emergency”…
Of course, there is no actual logic to any of this, regardless of actual logistics.