But I think this raises the issue of what market is CC trying to serve. Is it a business market or is leisure market service ? If the former, then it’s more likely that the destination station (or the city business district it serves) is the actual final destination. But if its leisure it maybe more likely that the final destination is further afield than a city business district, and most likely necessitating a change of transport (mode) anyway ?
I don't think any such analysis will help. The current Cross Country set-up is used for a variety reasons. Personally, I have used it for holidays (Reading-Newcastle as part of a Scottish trip, to get to Southampton Airport for a flights, and in my youth, before it was a thing, equivalent services for holidays in Scotland and Dorset starting from Reading), business (mostly to get to Birmingham, Wolverhampton or Manchester for meetings), family visits when my in-laws lived in North Yorkshire, and commuting, when Cross Country still ran to Gatwick and Portsmouth and sometimes it was a convenient (and much more comfortable) way to do the Reading-Guildford part of my commute.
I think that this misses the point. It's not just an end-to-end service for grannies in Manchester or Newcastle to go the seaside at Bournemouth or Torquay. It is a very useful service for all kinds of travellers using various parts and various lengths of its network. The main cause of complaint repeated on this forum (over-crowding) shows that there is more demand for its services than can be coped with by its current capacity. Small fixed-formation 4- or 5-car trains are no longer sufficient.
You may also call the Swansea -> Portsmouth and Brighton service (as it was) Cross County, and Liverpool - Newcastle ... under GBR▸ ▸ there is some logic to move things between logical divisions for today rather than for the last 30 years. Might add the Marches line too.
This highlights a confusion. Are we talking about the current Cross Country franchise operation, based on long-distance services running largely on an X-shaped network linking Scotland, the North-east, Yorkshire and the East Midlands (on one arm), Manchester, Cheshire/Staffs and Wolverhampton (on the second), the Thames Valley and the Solent/Greater Bournemouth area (on the third) and Bristol and the South-west on the fourth, and a "tail" to Stanstead, all radiating out of Birmingham? I can see the sense of these remaining as a single business unit, with a common core fleet of trains and staff, into which the other routes you mention do not seem to fit well.
Or do you mean that under a new unified GBR, they ought to be promoted together as part of a strategy to encourage more rail use by long-distance travellers not intending to travel via London? I can support this, as over many years I've been surprised by how few potential passengers are surprised to learn (for example) that there are direct trains from Reading to Gatwick or Manchester. But I cannot see any advantage or possible improvement to the trains on the current Cross Country routes from lumping them into the same operating division or business unit.