Connections
I do not see why the BHX route could not be 2 x daily year round.
Flybe operate multiple flights from BHX to GLA, EDI and BHD. Aberdeen is also 3/4 daily.
Connections could be offered via BHX to all these destinations morning and evening.
This has worked before at Exeter where connections were offered via BHX to these destinations until Exeter was able to sustain it own direct flights.
Just an idea.
Centre cities