It might be possible to justify waiving some rules, but when open competition is waived, it's almost always for a sleazy reason and frequently ends up in litigation. You should be suspicious of this move, not excited about it. You won't be suspicious of it, because it's Trump, but you should be.
I'm fairly convinced almost no deal gets done without some sleaze politician benefitting from it financially with or without oversight. I had hope's that this country would never get to a place where one person would have the power to legislate with a pen and dont like it. Obama opened pandora's box and did it with a vengeance. I dont want Trump do do it either.
HOWEVER, we have a democratic party who is willing to do any and everything in its power to block the building of the wall simply for political gain. I am so 100% behind the wall construction to drastically reduce the flow of illegal migration for both fiscal and national security reasons that I am ok with this project getting done by whatever means. Otherwise it wouldn't get done. I can't think of another construction project I could support in this way.