The other problem is that at the moment the main traffic flow on that route is Bishop - Darlo or Darlo - Teesside (aka Boro) cutting back those services might mean reduced traffic on these trains.
It's hard to suggest (realistic) improvements without making *something* else worse, but the Saltburn - Bishop Auckland service is a bit of a muddle at the moment.
Half hourly from Salrburn to Darlo, but only (approx) bi-hourly to Bishop Auckland, meaning a number of trains (from Saltburn) are sat in Darlington for half an hour or more, waiting for the next path east.
I appreciate that units need some recovery time and can't work flat out all the time, but it does seem wasteful. Hence my idea of concentrating the Saltburn services into a half hourly shuttle as far as Darlington (leaving Bishop Auckland to a separate service to Darlington). No change for Darlington, which retains the same service to both Middlesbrough and Bishop Auckland.
Since the ATN service from York to Sunderland was withdrawn (both the TPE extension to Wearside via Newcastle plus some York - Yarm - Hartlepool - Sunderland services), Sunderland lacks direct links to the ECML (there are a handful of GC services, but not a lot). So, I was wondering whether a direct Darlington - Hartlepool - Sunderland service would work (with ECML connections for places further south at Darlington). Possibly couple this to the Bishop Auckland service to tie up two loose ends.
Ideally I'd have the York - Hartlepool - Sunderland service hourly, but GC would (understandably) concentrate on London services.
Not perfect, I accept, but a suggestion. Another suggestion would be to extend the train shed at Darlington to cover the "avoiding" lines and ensure plenty platforms (since the Bishop Auckland services have to fight for platform space with the five/hour from York to Newcastle).