As others have said, the only attraction of CWLCY is if you are close by to start with or can more easily connect there. The service used to be more attractive when it gave 210TP but that is long gone and I prefer UD 744 to the A318 seat.

Now, if after pre-clearance in SNN, BA1 would empty into JFK T7 for connecting flights on AA without needing to go landside and clear security again, it would be a different proposition altogether.