Only thing I could think for the 1 & 1A with the PVR going to be either 16 or 17 vehicles would the the Coaster getting B9s from the TVT when the new vehicles arrive and the B5LHs either go on a route such as the 58, Blaydon Racers or are moved away to another Go Ahead division.
6084 would remain at Riverside as a spare for the TTX so that would mean 6071-6083 + 3x or 4x of the best ex TTX batch examples getting allocated to the Coaster with the other 2x acting as spares for the Coaster & Cobalt Clipper.
RE: Go North East: Upcoming Service Changes v2