Other than the fact that Scotrail are trying to secure the off-lease units for the short term, the fact that the 16x and 365s really don't have that much in common beyond looks makes it a bit of a non-starter. Plus the fact that it only acts as a short term solution, the 769s, whilst not perfect, allow the bulk of the turbos to shuffle off westwards to help improve the service there.
Trying being the operative word. Who’s to say they’re the only interested operator?
And the 16x and 365s have plenty in common - doors, brakes, suspension, running gear, control electronics are all very similar, if not identical. Plus a fair amount of the groundwork for GW getting 365s was done a few years ago when they were due to be cascaded 365s. Floor heights, and thus stepping distances are the same as 16x; so platform works will not be required.
I just don’t see the 769s making any useful impact into Turbo cascades. They can’t replace Greenfords. They can’t replace Marlows. They can’t replace the Cotswold units. They’re completely unsuited for the North Downs both mechanically and internally. They perhaps - just about - make sense on the Henleys, Windsors and Basingstokes. So we’re going to replace 4 (+1 spare?) Turbos? I just don’t buy it. 5 Turbos isn’t going to make a meaningful contribution in the West. And Crossrail will release plenty of 387s to other duties (on top of the 12 for HEX) once that starts in Dec 2019. Are the released 387s really going to sit around idle then?
Read the press-releases. “GWR has also sourced additional rolling stock to release the Class 387s for the modifications, ahead of the start of Elizabeth Line operation to Reading from December 2019”. Nothing about a Turbo cascade. Something short term, to enable 12 387s to receive HEX modifications. 365s would make a lot of sense. 319s - perhaps. 769s? Why would they need to be lumbered with a Diesel engine? They’re a Solution looking for a problem to solve.
Maybe I’m wrong; but it’s rather telling that the only planned operators of 769s have had them foisted upon them by the DfT. Not one operator has actively expressed a desire to have them - Porterbrook damn near cancelled the project before the DfT got involved. What does that tell you about TOCs opinions of them? Why, in this private venture, would that suddenly change?