I do know from my own job that some passengers will go completely out of their way to avoid changing at New Street and what's more if the operator offered cheap fares it could tempt people a bit more
That’s the problem in these threads. I Don’t think that anyone “enjoys” changing at New Street, I think we’d all prefer a direct service to our destination instead of one that dumps us at a bewilderingly big station (especially because people unfamiliar with modern Birmingham may still think it’s the dirty/ unsafe hole in the ground that it felt like in the 1990s, perception matters)
However, the limited number of paths available through the tunnels (and a West Midlands generally) means that we currently have paths for (just?) two trains per hour from Merseyside/ greater Manchester/ Yorkshire/ Nottinghamshire/ Leicestershire/ Thames Valley/ West County and one from Cumbria/ South Wales (all of this is based on the pre-covid timetable because that seems the fairest definition to use but happy to pick another if you’d prefer?)
Now, if we try to adopt some consistent definition and say that “north” and “south” are based on the tracks that services use to approach New Street (I.e. the Stansted route is therefore “north” of Birmingham), then that’s eleven from the north versus five from the south, so it’s not possible for everywhere to get a cross-Birmingham service
As you’ll see, some through journeys are possible, some aren’t, there’s no real reason why Basingstoke to Stoke on Trent is a through train, or Alnmouth to Plymouth but not Alnmouth to Portsmouth - just coincidence
You could probably tinker with each of the routes further away from Birmingham but it’d generally be robbing Peter to pay Paul…
…you could have direct services from Portsmouth by extending the bi-hourly Reading terminators but any laudable plan to run Birmingham services to places like Middlesbrough/ Hull/Bradford would be at the expense of some Newcastle trains…
…more Leeds trains come at the cost of fewer Doncaster trains…
…giving Chester a proper fast Birmingham train via Stafford (rather than the painfully slow Welsh service that now goes via Shrewsbury/ Wrexham) would only happen if you cut the frequency to Liverpool…
And even if you did decide to reduce the frequency to Newcastle/ York/ Basingstoke/ Southampton by introducing an hourly Hull to Brighton train then it’d still mean changing at New Street for a journey like Hull to Cardiff/ Bournemouth or Liverpool to Brighton, it wouldn’t mean that Hull and Brighton had through trains to everywhere
(There’s also the problems of trying to match up EMU routes - one day we’ll have sufficient bi-modes but I don’t like running diesel trains under the wires from Birmingham to Manchester - trying to match together trains of similar lengths - the Cumbrian service is often a nine/ eleven coach electric 390 so winning some kind of “nationalist” kudos by running that onto the two/ three coach diesel Gloucester trains to provide regular direct trains from Edinburgh and Glasgow to Cardiff has obvious flaws… plus the reliability issue of keeping such a long distance service on time, assuming you could get paths into and out of New Street St similar times)
Maybe there are some flows where enough people would genuinely do long distance journeys often enough but I think that the fact that the Aberdeen-Penzance train links Inverkeithing (for Rosyth) to Plymouth (another naval place) is coincidence, rather than shy huge market of long distance Sea men
I think that some people want a timetable where everywhere in “the north” gets direct trains to everywhere in “the south” but this kind of markets are best served by National Express etc, the “put your Granny on a coach in Swansea and it’ll take her home to Peterborough” journeys aren’t going to sustain train services, they tend to only happen a couple of times a year for a start
Focus on giving all significant corridors a frequent/Reliable enough service to Birmingham, if it matches up with something on the other side (e.g. hourly/ five coach / diesel) then you might get through journeys but that’s a “bonus” - living in South Yorkshire I’d be fine with all of our trains terminating at New Street if need be, or running to Cardiff instead of Plymouth, as long as we retain the half hourly Birmingham frequency that we currently have
Same applies to services from significant corridors into Manchester/ Leeds etc, people get rather hung up on things like whether Middlesbrough trains should run through to Manchester Airport or to Liverpool, but the important thing is that Middlesbrough has a decent enough service to Leeds (and to a lesser extent to Manchester), after which any additional stops are a bonus, we can’t squeeze through direct trains from everywhere to everywhere
As for your second point about how you’d need to keep it cheap, yes, you would, but at the same time you’re not taking on a share of an existing busy flow (GC/HT had a share of markets like York/Doncaster to London from day one so knew that there was some guaranteed revenue… whereas you’re in the situation where your fares are going to have to be so cheap that I genuinely don’t know if you’d break even with every seat taken -beating in mind how expensive a lot of XC fares are and busy their trains are yet they still need subsidised - Megabus seem to have successfully evolved from being a “£1” operator to charging briefly in line with National Express but trains are much harder to operate and if you’d only make a profit if you pretty much sold every seat on board then that’s a very dangerous game!
It also raises a supplementary question, is the management mindset different at the OA operators. After all if the trains dont run, or are not well patronised the operation fails, quickly, and with no bailouts. Contrast this with TPE or Avanti, dreadful service now for an extended period of time, but still in business.
One of my fears of nationalisation (which Northern’s abandoning of a few local routes in Yorkshire hasn’t dissuaded me of - if Arriva had behaved like that then there have been outrage but because it’s all government controlled people merely accept these cuts)