I'd agree with most of that but it wasn't just the safety interlocks the need to redesign the B turret down to 2 guns was also a delay to the ships. Also correct me if I'm wrong but didn't the quads have problems with accuracy as well for some time due to shell interference?
The 14" were good guns but I'd have to think that the RN would have been better served not having to make another new gun design and instead be able to reuse the 15".
But yes the KGV's were there when needed and were a good enough design based on what they knew at the time.
I'm not aware of any accuracy issues regarding the 14" quads, but I cant access Navweaps or my referance books from work, I belive that the guns had a wider spacing in comparison to the Richelieu class which did have dispersion problems untill delay coils were fitted after the war.
The 15"/L42 Mk1s could not be reused in a 40° degree turret due to the position of the trunnions in comparison to the 14"/45 Mk7 if i remember correctly, I'm not sure of the exact reason but I belive it would require a higher profile turret in comparison to a new gun because of a greater clearance needed below the gun to elevate it to 40°, also I wonder if the tendancy of wire wound guns to droop would be increased at higher elevations.
It's not just the turret design but also the shell handling equipment and magazine arrangements that would need to be rearanged, would bigger magazines be needed to fit the required number of shells, what needs to be moved to accomodate it, do you need an increase in beam to allow for the greater weight being stored in the ship and the increased weight of the guns in the turret as the 2nd quad had a detrimental effect on the stablity of the Design so a triple in that position may once again compromise stablity.