Too much like a locomotive!
It also allows them to shortform trains when short of units, which is cheaper than having a large enough fleet to cope with traffic levels - and stuff the passengers.
The problem there is, the Chiltern NIMBY brigade would rather set the entire Chilterns ablaze to "save" it from the "menace" of the railways before accepting progress and the passage of time. If the NIMBY brigade kicked up such a stink over HS2 despite that being mostly out of sight, I can't even begin to imagine the hyped up tales they'll tell about "anxiety" over seeing a wire at 50,000 paces; all supported by the Daily Wail printing headlines such as "SHOCK HORROR RAIL ENGINEERS DESTROY THE SIGHTLINES OF THE CHILTERNS" or words to that effect for months on end.
The railway will have permitted development rights though, so much like the Goring nimbies there won't be much they could do about anything within the railway boundaries.
Both are possible, but probably not necessary. For fuel tank capacity, it depends on how much of the intended routes is electrified. In East Anglia, for some diagrams it is very little, so if there is more electrification on the intended routes than on the rural East Anglian routes, it seems unlikely fuel tank capacity will be an issue.
This kind of ignores what I suspect would be quite a major part of the consideration: the costs of the units to be ordered.
Their power to weight ratio is 16/17 kw per tonne which is far above the 185's 10kw per tonne so I'm sure they would be fine. Even the lack of gangways I doubt would be a problem, it's all about fuel tank range which I'm sure Stadler could increase with a revised design.
Besides Switzerland, their largest orders first came from various German operators in the early 2000s, before the GTW evolved into the FLIRT which was rapidly ordered by MAV in Hungary, VR in Finland, more German operators, VY in Norway, plus Polish and Dutch operators.
Is that on electric or on diesel? and just checking that is for the 3-cars, as the power-to-weight ratio is different for the 3-car and 4-car versions, as the 4-cars have double the diesel engines compared to the 3-cars.
GTW was popular in the Netherlands for a while too, though it has been overtaken by the FLIRT!
The 16/17 kw per tonne number is for the 755/4 on diesel, which has 4 engines for 4 cars, the /3s have 2 engines for 3 cars. On full electric, they are even faster, but drivers don't apply full power anymore like when they were new. According to Wikipedia on full electric, 755/3s are quicker as they are lighter:
Oh yes, if only for an electrify and cascade.......
I'd think it would be fine for Carmarthen/Swansea-Manchester for example, as both Crewe-Manchester and Cardiff-Newport are electrified, which are significant stretches where a FLIRT wouldn't use diesel. Cardiff-Holyhead might be more challenging, but even there the Cardiff-Newport electrification would be helpful, and I suspect it would be fine though some detailed modelling using data from both the GA and TfW operations with 755s and 231s would probably be advisable. It would even be possible to run some of the more demanding TfW IC diagrams with some 755s (and a TfW driver route-conducting a GA driver) as a test, and see how they perform and how much fuel is left at the end of a full day. But just to re-iterate, I strongly suspect it would be fine as long as they pan-up where OHLE is available.
I can't see that being much of an issue on the Marches - if it's an issue for FLIRTs it'll be an issue for the existing loco-hauled trains.
Where though? Landore?
The issue appears to be trying to maintain too many (56) at a depot with limited space, with limited staffing, on a train that appears to be of cheaper quality build, along with a shortage of parts.
Or alternatively another order might give them the volume to justify a south Wales maintenance facility (or it could be a condition of the order).
)
Notwithstanding that CAF has been shortlisted for the Northern and Southeastern new train tenders, for which (partial or full) level boarding is a requirement.
That's a question of Investment, and if ordering more units (or even ordering just additional centre cars) then investing in capacity.