IMHO, in terms of the current TOC setup, Stansted/Leicester/Nottingham-Birmingham should be with EMR, Birmingham-Cardiff with TfW, and Norwich-Liverpool is correctly with EMR. They are ex-Regional Railways/Central Trains routes, after all. I think a trolley service of drinks and snacks is adequate for those services.
As for the 'Voyager' route network, I'd be sorely tempted to chop off the north of Newcastle (or even north of York) branch plus Cornwall and use the freed-up rolling stock and crew resources to boost train lengths and frequencies on the core network where XC is the main longer-distance operator. Sure, you'd lose some revenue from abandoned sections (to other TOCs), but since everyone seems to be complaining about overcrowding on Voyager services, you should be able to make that up from carrying more customers on the core network.