I thought a lot of the problems with the MRA 4 was to do with trying to get computer designed wings to fit on hand built fuselages and sticking engines that hadn't been designed to operate down long ducts, down long ducts.
They would have been better building new Nimrod fuselages, but computer designed, it would have probably worked out cheaper.
I remember reading an article that when building the Nimrod wings the first time around, you needed someone in the wing, in case f emergency there was a cupboard next to the aircraft with a stone cutter jobbie in to slice through the wing if you needed to get him out!