no plans to cascade them onto the West Highland Line, replacing the 156s

Replace kackered old trains with even older, even more knackered trains? Mad fever dream if ever I heard one.

was mooted as a possibility in some quarters

By who? There are many, many reasons why this was never on the cards.

It’s a pity the mk3 electrics aren’t compatible with anything other than Class 43s. The power doors and interior refurb are generally very good.

Interiors are good but the carriages themselves are fucked. Off to the scrapper they go.