In defense of Stobart, the facts are that their Aer Lingus Regional business has been successful and noted as the better piece of Stobart Group's portfolio in recent times. Airlines mostly everywhere have been immeasurably impacted by the pandemic and only a few are financially strong enough to weather this storm, and others get bail outs eg Lufthansa. The business will come back, timelines are unclear. So whether Stobart for a recent bailout of not is a mute point.
Airports investing in airlines is not customary, however if the owner of BHD did invest on commercial terms that's another matter.
I don't believe that the above investment scenario is on the cards. The fundamental issue here is about the brand and distribution. The EI contract has very limited time left, and its been publicly stated that EI will pursue all avenues in terms of the right airline for the franchise. What at this juncture is in it for Aer Lingus? Unless BHD has given concessions to EI on operational costs? These would apply to BA, under the IAG procurement umbrella. There is limited strategic value for EI in expanding the EI Regional brand at BHD. They add value feeding passengers into the TA network.
As a consequence Stobart will need to build a new brand for BHD. This doesn't sound promising to me. However, as a counter balance, encouraging to see BHD regaining some lost services via Loganair, Eastern and BA.