IAG approach
I was just reading a very detailed article online with compelling analysis of the competitive position on the Atlantic by carrier.
It explains that the Irish government may seek assurances on the Aer Lingus slots at LHR, as would be naturally expected. However, by simply stepping up aircraft size to 321's across the board on EI services over 320's and 319's, the seat levels could be maintained and a batch of slots in the bag.
Equally at Belfast City post a take over by IAG, there is an opportunity for consolidation and a move from 9/10 319/320 operation to say 6 321 services.
The net effect of these suggested changes to DUB LHR and BHD LHR could net BA 10+ slots per day while satisfying the Irish Government.