Washington does seem flavour of the month!
Here's my suggestions.
I'd reduce all services to Heworth, apart from the M1 (and a new express) but have regular buses connecting at key points along the out like Concord and The Galleries.
I like the idea of circular services, maybe having an inner circular and an outer circular, with the M1 operating through the core, North to south and the 8 & 50 East to West.
Inner circular 15 min frequency. Galleries, Albany Village, Blue House Lane, Concord, Spout Lane, Barmston Centre, Village, Brady Square, Biddick, Galleries
Outer circular 15 min frequency. Concord, Blue House Lane, Blackfell, Oxclose, Galleries, Lambton, Ayton, Rickleton, Harraton, Fatfield, Biddick, Galleries, Glebe, Barmston Court, Teal Farm, Waterview Park, Nissan Service Roads, Sulgrave, Concord.
New express 30 min frequency. Newcastle, Heworth, Concord, Sulgrave, Glover, Waterview Park, Castletown, Sunderland
Birtley connections (20 min frequency) maintained by a Chester, Birtley, Portobello, Vigo, Barley Mow, Ayton, Lambton, Galleries (peak time via Crowther and Oxclose to Galleries and onward to Waterview Park).
This maintains the hub and spoke method GNE favour whilst opening up new links to key employment sites. All villages have a service, with regular onward connections to town and city centres from Concord, Galleries, Nissan and Waterview Park
RE: Service Suggestions