seeing as Jet2 has stolen their thunder they could try PLY-BOH-EDI.
EDI would work well from BOH. Especially at their fares. not so sure about PLY though. Only a two and a half hour drive away.
If Air Southwest did come to BOH I think it would make more sense to base an aircraft here and launch a number of routes.
Edinburgh, Jersey, Guernsey, Manchester and Newcastle all spring to mind.