EASA-OPS hasn’t stated that mid point can substitute touchdown RVR for several years. What it does say is that one transmissiometer may be inop (assuming you have multiple to start with) for cat 2-3A and just one on the airfield for cat 3B. Thoeretically you could land cat 3B on 18R in AMS with no working transmissiometer on that runway but an RVR reading from runway 27 that is above your minimum. Also, assuming you need 200/125/75 for a cat 3A approach, you could have inop/125/75 and legally continue to minima.