I do not claim any wisdom on this matter. However I could lay claim to such wisdom as may be attributed to years of life and associated experience
I have (no doubt slective) memory of BR days, well before its 'Balkanisation' as seen in this posting: XC, SWR, GWR, GA, Scotrail and TfW (and the rest); these matters were immaterial, tho 'Regions' and their basis in the 'Big 4' pre-1948. There always will be need to consider best use of stock, track, crew etc in relation to user (and potential user) needs. It's complicated.
GBR however offers opportunity to rethink provision without TOCs. Although change is unsettling and difficult to bring to fruition this is an opportunity on a scale that has not been possible to even contemplate for a long time. I appreciate that means a lot of opportunity for things to not go well. HS2, GW electrification, Castlefield, ECML 'new' timetable, give 'pause for thought' and loss of confidence. New Year is a time for renewed resolution, and boldness.
I think that proposals such as this, crayonistic as some may label them, are worthy of serious consideration at 'HQ'.