Why not delegate the border infrastructure to the Corps? Is there any really sound reason not to? Obviously need vs. want is a debatable policy factor in terms of any wall planning. Aside from that and presuming a wall will be designed and built, why use privateers instead of the Army Corps of Engineers?
The Corps does big-time water irrigation and flood control projects, maintains and enhances navigable waterway infrastructure, and has the size and expertise, given adequate funding, to do the wall job without marking up costs to inflate profiteering.
Give the Corps the jurisdiction, then stand aside as they'd do the job. Trump should have the legislative votes needed; the Republicans want the wall and many western Republicans are keen on their water projects. If the Corps is best for river commerce and massive crop and livestock irrigation spending, why not for border infrastructure?
Again, whether a wall is needed is a separate political question from how one would be most efficiently financed and built.
Use of the Corps would moot all trashy politics of who'd get to make big money off the adventure. Bechtel and Carlyle Group intentions and shenanigans are part of history in recent regimes (dating to pre-Watergate times), but big infrastructure profiteering need not be a perpetual handmaiden to government policies and services. Halliburton's excessive profiteering off Iraq discredits forever the notion of various well-placed politicized defense contractors having a hands-off entitlement to fleece the government. No such entitlement exists, and if a border wall is to be built, Halliburton-in-Iraq levels of ineffectiveness-for-profit are not needed, and would be undesirable on ethics grounds.
Just as government could better provide a close management of the nation's health services, the Corps like the VA gets the job done, thereby proving the private sector is but an option, and not necessarily the best one, while certainly not a necessity.
Instead of the Corps, who? That two-man venture out of Montana that got the Puerto Rico electric grid contract? Left to Zinke and the Republcan will, the two Whitefish Montana contractors would have a better shot at things than the Corps? Presently? Yes/no?
One last observation and readers can look it up. Effectiveness. Gen. Leslie Groves managed the military's building of the Pentagon and after that he was picked to run the Manhattan Project. With that in the military's resume, grounds to discredit government project management efficiency fail to exist.
There's a track record in those two mega-projects that the private sector cannot match. Moreover, when the TVA and Bonneville power projects happened, it was federal involvement at all levels of the rural electrification program that made it work as quickly as it did, pre-WW II.
BOTTOM LINE: Don't ignore the Corps.