Whatever change you make is bound to upset someone. If I've understood your suggestion correctly, Leeds would lose direct services to Plymouth/Penzance via Bristol and gain direct services to Reading/Southampton via Oxford.
Quite, but those travelling from North of Leeds would save 20 minutes on their trip to the Midlands and South West. The conflict will always exist when a TOC serves such a wide catchment area.
It's of course possible that DfT and XC may have statistics to show how many are currently travelling from where to where. Use of split ticketing probably complicates such analysis. The advent of TPEs extended services beyond Newcastle will further confuse comparisons.
At present I notice large numbers changing at York, Leeds and Sheffield, but not so many at other stations.