There were loads of ways you could've done it without majorly changing routes or having a lot of dead mileage for buses and driver changeovers...
Some ways could've been
X7 - No Change to route but interworks with X9
X8 - No Change to route but interworks with the X10
X9 - Divert via Brunton Park
X10 - Divert via Brunton Park
43 - Extend to Blyth following the X11 route. Longer journey to Newcastle but improves overall connections and doubles the freq. Map
44 - Divert via Hollywood Avenue.
45 - Divert through Jesmond to help with economic viability. Map
46 - Cancel this route. This route can mostly be covered by changing the X9 through Brunton Park
52 - Extend this to Ashington from Cramlington and slightly change the routing after the Freeman Hospital. Map
53 - Extend this to Morpeth in place of the 43, this will then interwork with the 2. Kirkhill would be served by the 35 instead. Map
54 - Minor changes to routing. But interworks with the X7. Map
55 - Reduce the frequency to every 30 mins but upgrade the route from solos to singles (this could be interworked with X7/X8) Map
56 - renumber the 57A to better fit with the numbering
57 - extend both the 56/57 to North Shields via Marden covering the lost links from the 306. (But it is not essential, as the 1 also does this.)
306 - Terminate and do a loop of Tynemouth. There is no need for this service to go through to Whitley Bay just duplicates everything. Map
308 - Turn right after NT Hospital and divert through Marden to give better buses for this estate. Also differentiates it from the 309 better.
Below is a rough overview of the routes, I did not include everything mentioned such as the small changes to 306/308.