The strongest category is CAT IIIc and the need for visibility is not existent. The so-called decision height for landing is also not existent. IIIc is not in use though, so I to IIIb are used.
Yes, but per your very own article the only reason IIIc isn't used is because taxiing blind is impossible. There is only one situation that a plane would land IIIc without a windshield and that's if its cameras failed. If all of its cameras failed then it's an emergency landing situation anyway and they could clear a runway and tow the aircraft into the terminal like they often do with an emergency landing due to mechanical failure.
In every other situation you would have at least visual and probably FLIR video.