minuteman
FR are an Irish airline because of:
a) low corporation tax
b) IAA rather than CAA
Once Poland or Estonia offer them a better deal, Ryanair HQ will be there like a flash.
The "fifth freedom" flights to Europe were back in the bad old pre-deregulation days when they needed the uplift pax to make the ex-DUB flight pay. With more efficient use of aircraft routes ex DUB and other Irish airports are now profitable.
As has been pointed out previously, EI's paring of UK regionals has damaged the possibility of feed from places like NCL, BHX, etc. to LAX, ORD and so on.
I think there is plenty of profits to be made from Irish airports - witness Arann, Baby, Jetmagic, Flybe, CSA to ORK - even BA to NOC! CSA are marketing their PRG base as a hub for Central/Eastern Europe ex ORK.
If IB want slots for LHR there is always leasing. Taking on LHR as a base only invites retaliation from continental carriers, and that's a fight EI doesn't have the money to win.