Think the biggest indicator whether Arriva will be able to invest for Northumbria & Durham County will be the impact of the ABTRL when that opens.

If Arriva were going to order now based on no impact (which I'll doubt will happen)

Option 1:
- 12x E400MMC to replace 7541-52
- 7541-52 either cascaded to Blyth, or Darlington for the 7 with further classic E400 cascades as a result

Option 2:
- 22x StreetDeck for Blyth (X7/X8/X9/X10/X11)
- 43/44/45 and 306/308 allocated 64/15 plate E400s, 61 plate DB300s and a small selection of 59 plate DB300s. Depending if enough for spares, rest of 59 plate DB300s and also the 57 plate classic E400s put into a lesser role or cascaded.

Note that if Arriva did a StreetDeck order for Blyth, could also give scope to throw in some 6-Cylinder StreetDecks for the X93 allowing the B9TLs to take a backseat role and help out with the summer loadings / timetables.