It would probably be better if the X83 being once an Hour and then keeping the 15/15A the way they are currently.
With this I was just looking at Timetables of routes I hadn't photographed and looking at it on Paper it just seemed to click into place perfectly, plus the 689 is more Frequent on a Saturday also if I think.
As for the 50A surely it can't be that bad as from Boldon it would follow the same route as the 9 to North Shields. But to perhaps improve Reliability between Chester le Street and Washington have go straight up the Motorway and again Between Washington and Boldon via Concord and Waterview Park as it does currently on a Night.
RE: Go North East Service Suggestions