I'll admit I didn't wade through 12 pages before posting. In what way are the LNER sets more compliant than the EMR sets? I couldn't see much difference other than different seats and colours.
From memory it's mainly the grab handles, as well as the accessible coach in the ex-LNER sets (formerly coach F) with a UAT, which is missing from the ex-EMT sets.
How is it possible that the mechanical state of the LNER was not known? Someone must have known. Was this not considered before the plan to move hem to EMR was formed?
From what I gather, the decision to go with the ex-LNER sets was made quite late in the day, at which point LNER were running them into the ground/towards mileage exams, whilst EMT/R were busily updating their Mk3s with new window glass, etc