Can any of you guys put a link to the EUOPS where this issue is laid down?
And (this is to the veterans) Does anyone know the history of the approach ban concept?
I would say the approach ban concept is avoiding the danger that means airplanes flying approaches with very low probability of success and a not so low probability of "temptation to fly just a little bit below minimum". If the event that RVR goes below minima after a given point in final, then you can wait till the DH to discontinue the approach.
With no DH, if you can only continue and land, even in zero zero RVR. Why don't they just establish CAT IIIC?
Besides, if you land with nearly zero RVR, you will have to wait in the runway centerline until RVR increases. No one else can shoot that approach after you, in the mean time.