Ah, new Diesel engines on the UK network...
Ponders the possibility of a new 2/3/4 car DMU order !
Although shorter, suburban DMUs probably won't require 940hp power units as are being fitted to the IEPs!
So presumably there's now a diesel engine that meets emissions regulations and can fit under the floor of a vehicle that will fit the UK loading gauge? That's an extra positive from all this. Perhaps Hitachi could also come up with a viable low-cost pacer replacement that would keep it's new factory busy once the IEP order scales down.
Given that a 142 has a total of 450hp, a scaled-down version of these power units attached to a modern, lightweight bodyshell would be ideal- even decommissioned engines from converted bi-modes could be used, perhaps with just one engine per 2/3-car unit?
As things stand with the HSTs/Meridians and now Mk4 sets being usurped from their current duties (along with 185s too) means that we'll have a surplus of high-powered/intercity rolling stock which is not ideal for cascading to lesser routes. Even 155/6/8 units are used on services that they aren't ideal for in terms of dwell-times: Huddersfield-Leeds for example being more suited to stock with doors at 1/3 & 2/3 rather than at the ends of carriages.
To get vaguely back on topic, I can't see the Mk4 sets being sent to the scrapheap- The obvious candidates would be MML or GEML services, but perhaps the London-Cornwall services would be good too- Running them with the 91s until the wires run out and dragging onwards with a 67/68? That might even be a solution for future London-West Wales services...