There's an interesting discussion here. Could GBR bring Cross Country DOWN to the standards it experienced under British Rail?
Presumably some people have (conveniently?) forgotten how bad it was in the BR days. After all, Virgin named their transformation "Operation Princess", given how much of a "Cinderella" it had become compared to the rest of InterCity
Irregular trains, complicated routes, BR's Cross Country was only really attractive to the demographic who were willing to wait all day for the one direct train between some far flung places (great for the "stick granny on the train" market, but most people won't base their entire day's plans around it)
It was like a train service designed by a committee, trying to tick several boxes and therefore not much use as a service to most, reminiscent of the kind of meandering bus routes that councils used to run forty years ago.
(In fairness, it was occasionally useful for me as a student, the kind of person you might now call "time rich but cash poor", able to base my plans around a daily service, but that's not how most people will want to travel in the 2020s)
Birmingham to Bristol meant a reversal at Gloucester*
Birmingham to Preston/ Glasgow saw a significant amount of trains threaded through Castlefield to try to additionally tick the "Birmingham to Manchester" and "Manchester to Glasgow" boxes), or even via Lime Street to tick the "Liverpool" boxes
A simple journey like Sheffield to York saw many trains running via Doncaster AND Leeds, to try to serve those markets, making the railway an unattractive option
Edinburgh only had three (?) Cross Country trains a day to Newcastle etc - essentially placing journeys for the handful of Craigentinny HSTs (much like the way MM/ EMT only really served Leeds because some of their stock was based at Neville Hill
It was a mess, and had been for a long time. Great fun for certain enthusiasts who enjoy quirky services, but well past it's sell by date
But maybe there's something to be said for dumbing down and going back to the BR days of 90mph trains (remembering that it was mainly operated by 47s, some 158s, plus also some HSTs, a handful of 86s), for the simple reason that it would have been much easier for the franchise to obtain new (or cascaded) stock
Great though the transformation was, vastly speeding up journeys, increased frequency etc, creating a timetable based exclusively on 125mph tilting diesel trains effectively forced XC into decades of being stuck with Voyagers (the government wouldn't back the plans to extend them to a proper length, Bombardier didn't have the jigs any more, not a lot of second hand trains capable of matching Voyager paths - AIUI the token number of HSTs that Arriva got had to be kept to paths avoiding certain stops to help them keep pace with Voyagers)
Virgin were a victim of their own success. The boost to passenger numbers (when you increase frequencies, simplify timetables, speed journeys up) meant something needed to be done to keep the virtuous circle. Instead, the government wouldn't back them (and Branson/ Souter were understandably reluctant to purchase specialist trains for the Management Contact that HMG had converted the franchise into in 2002)
In contrast, Midland Mainline (who inherited another neglected bit of InterCity) had a similar initial investment but were then allowed to replace their two coach 170s with three coach examples, then replace these with four coach 222s - imagine if VXC had had similar sustained backing?
If Virgin had gone for something less-flashy (less fast, less tilty), like four coach 170s, it'd have been much easier for them to order new trains from the conveyor belt of Turbostars that were being built over a decade or so (175s etc if you'd prefer), or at least competed for any potential cascades of DMUs like 158s. Short formations might have been dealt with incrementally (much easier to keep marginally increasing your capacity to match demand if you've a bigger range of trains to choose from)
However, given the way that Cross Country interacts with most major lines, once their timetable was built around 125mph tilting stock, there was no way back, no scope to tag on to orders of other DMUs
They were stuck with specialist DMUs that they couldn't easily replace, with timetables that would only have worked with trains that were equally specialist (and that's an operation that went from only around five years of being a proper franchise to being a Management Contact to being kicked into the long grass under Arriva, too tough and expensive for anyone to do anything meaningful to, which seems a recurring theme of Cross Country)
Laughable though the 158s may have been for long distance journeys, maybe keeping standards DOWN to what they were under British Rail might not have been such a bad idea, and a 90/100mph operation might have been better in hindsight
(* - Did some services go via Worcester too, or was that just the Provincial trains from Birmingham to Cardiff?)