// who's going to build that [hard border] then? //
Who knows how things are going to work? At this point it's enough to realise that, absent a sensible and mutually-agreed deal, then there will *need* to be some sort of Hard Border to deal with the customs arrangements. The point is then not to build this, because nobody wants to, but to accept that this is a place we can end up if we're not careful.
"Project Fear", in as much as it was, was not a threat or even a promise, but a warning. As soon as people start paying attention to warnings then they can avoid the danger.