As I understand it, it's B or bust for the Italian navy
Yes, only STOVL will do for them as far as the Cavour is concerned. After Harrier gives up the ghost it's Cool-Fanned Luke or rotary. Must be a bit of a worry, but then again, they are not short of other things to worry about so maybe they're just taking it in their stride.
I haven't seen any details of the new requirement but their original quota was 69 F-35As and 62 F-35Bs. The navy was down for 22 of these B's and the airforce 40, plus the A's of course. I don't know how interchangeable the B's were intended to be between the navy and the airforce, but presumably there would be flexibility.