I’d definitely want the border patrolled. Not sure what you mean by your first sentence.
I mean, if they are going to get shot at directly like that, I don’t see how the second barrier is going to increase the risk. Best escape still would be an acceleration in the direction they were already headed.
They could of course have bullet-proof vehicles, but double-wall barriers are pretty popular border designs for a reason.
(Alternatively, I wouldn’t mind filling the “moat” bottom with concertina wire and having them drive within the second barrier—but they would presumably need to have access to that moat space.
