Quite true about the bespoke nature of the airframes, but this was known about, or should have been, as exactly the same problem was encountered with the AEW some 30 years ago. Should have been allowed for in the MRA4 time frame.
Exactly - and how can the severe corrosion have come as a surprise? Aircraft spends 600 years (or so) flying at low level over the sea...does it really take the brains of an archbishop to predict that the airframe would be appallingly corroded?