Even if the Barricade is, like you suggested, a standard ward without a physical anchor, a chorae should nullify it. Maybe if it was a glamour, and they couldn't locate the spell at all, then that could protect it from being disarmed by a chorae. But we know that isn't the case. Mekeritrig knows where the door is, he and Shae stand in front of it on a small ledge off the horn, and Mek has been obsessively blasting away at the wards of the Barricade for multiple human generations. While his magics have been "missing" they haven't literally been missing the ward itself.
The Barricade-Field-Ward thing definitely fucks with space in some kind of crazy way. But they know basically where it is and it is acting on the forces Mekeritrig is throwing at the gate. It has to be acting on them or his castings would reach their target and act as intended.
So the big question is: why can't they toss a chorae at the area in which the ward is active in order to disarm it. The ward should act on the chorae just as it acts on Mekeritrig magics (it has to act on physical stuff as well as magical stuff or you could just walk through it), and that interaction between the ward and the chorae should destroy the ward.
I might be getting into the realm of crackpot speculation but here’s how I see it working.
Maybe the way it works is that while the Barricade and its workings are magical, the "field" it generates is not. The magical machinery of the Barricade acts on some mundane force and leverages that mundane force to produce the effects of the barrier. That way, there is never any direct interaction between the sorcery of the Barricades and the intruders/attacks that it repels.
Kellhus does something like this with his telekinetic barrier of debris to repel chorae. He uses magic to leverage mundane materials thereby creating a level of separation between his sorcery and the effects of his sorcery.
The mundane material Kellhus leveraged was debris from shimeh but what if the mundane “material” that the Barricades leverage is space itself.
Whereas most spells that alter space would do so by creating a magical distortion in space. The Barricades use magic to manipulate the medium of space without tainting it with magic. Emilidis, the artisan, found a way to use sorcery to bend space in such a way that the distortions in space he created were not themselves magical. He just moves the medium around. So the Barricades generate this field and its effects are not directly magical. The forces acting on intruders/spells/chorae are themselves mundane. Just mundane space twisted up in weird ways.
Actually, this works pretty well for Shae’s description of the Barricades.
“The Barricades,” he continues. “They fold… intervals. Somehow Emilidis found a way to pinch emptiness into angles. This was why no dispensation of sheer force could batter them down… In a sense, everything you and my predecessors threw at it simply… missed.”