Well, FR have stolen a march on EI for the winter and Summer 2022, haven't they? Its a little bit sad to see the EI base down to just 2 320s for the Summer, from the peak of 4x A320s and 3x AT7s in 2019. I see that TUI are selling their own flights to Reus, Lanzarote and Palma, which might explain some of the Aer Lingus reductions to Spain.
It will be inserting to see what happens to numbers to Manchester, fares and capacity will be good with FR. The 2nd service of the day is arguably a bit early, departing MAN at 1600ish.
Overall the departure boards aren't looking too bad for Summer 2022. KL and AF will be twice daily to their respective hubs, LX are back to ZRH 4x weekly. While there is no sign of LH to FRA or I2 to MAD, Volotea will be operating Verona weekly as well.
I tend to agree with what you are saying about EI Regional. Looking at where EI Regional flew beyond what has been taken up by Ryanair
The best options for any rebirth of EIR at Cork would be BHX and GLA. FR are operating to BHX, but at 3x weekly timings and frequency aren't the best, so there might be some opportunity there. As you say GLA isn't directly served but the service to EDI does cover some of that market. Connections to the smaller UK cities is going to be problematic without some EIR presence. SOU, NQY, BRS, CWL, LBA, JER, NCL have all been served by EIR over the years, with various levels of success.