As I said, bi-mode strikes me as an engineer, as the right answer. A purpose designed e-Voyager in fact.
It offers:
1) flexibility of go-anywhere, regardless of wiring spread progress and pace.
2) avoids the need for a wasteful specialised class of diesel locos that are inflexible in their location (especially coping with change due to electrification) and detrimental to current timetable times/frequencies through reduced numbers of powered axles. Nice theories about reusing the locos are fancifully wasteful as we have no shortage of modern heavy freight locos, they seem unsuited for freight anyway and all of that future use prediction is based on absolutely zero evidence or confidence it will be true on the day in the future - it doesn't survive the first moment's reflection of a business case assessement. Freed up engines on the other hand can have a virtually guaranteed 2nd hand usage - a few months back I was involved in the installation of a mixure of 2nd hand engines into a remote location generator facility in Afghanistan. There is a strong market for engines in this class to be used in a huge range of applications globally (especually where new, speialised solutions are unaffordable as is often the case in developing countries).
3) matches current 22X comfort wrt underfloor noise, an issue hugely over egged by obsessive enthusiasts and barely noticeable to 99% of travellers, whilst eliminating it on electrified sections. I travelled on a crammed 4-car 220 yesterday, luckily got a seat as the door stopped opposite me, and I completely forgot about it other than in the first few minutes when I was reflecting on this very issue. Underfloor engines are a non issue for all but a tiny minority of people, most of whom I suspect hardly use the services and who are thus of little to no relevence to the modern railway system and it's future. I also suspect if this was eliminated as per their wishes, they'd find something else to vociferously complain about instead as it is their nature that is the problem, not the train's.
4) The diesel system coming in at 5-10% of weight (less?) is irrelevent to being carried around, and the overall train is still lighter than peer EMU/DMUs, and much lighter than EMU+loco wrt track charges.
The overriding requirement on UK railways is to shift existing/increasing numbers of people and give them the seat for which they've paid. Not to reduce capacity and journey times or increase procurement (multiple classes of things) and operational (manning) costs.
Your proposals utterly fail to acheive the former, at the expense of the latter, all in the name of a specious and frankly unnessecry level of comfort that only you seem interested in.
It is better 100 people get a seat, any seat, than 60 get a seat much wider than they are and perfectly aligned with a window most wont look out of. We need maximum numbers of travellers to pay the fares, and to do what we can to keep fares down so the system is open to all. Not as you seem to intend, reducing capacity and raising costs so that only the wealthy can travel and thus give them a commensurate comfort level. If you want more space, go 1st class or use VSOE, or better still, start your own open access operator with the locos and coaches you love and see how quickly it goes downhill.
As I said before - I originally supported an EMU+loco. Now, I'm firmly in IEP & bi-mode camp. Perhaps you should reflect on the persuasiveness of your arguments vs. those of others, and consider that your "1950s in the 21st Century" railway dream has no bearing on reality.
Enough said.
(See, other people can also try and cut others off to give themselves the last word).
