I would think that most discerning business travelers, by which I mean those with the type of travel budget to allow them fly in “J” most of the time, will usually be transiting through the likes of LHR, FRA or AMS having flown with BA, SQ, CX etc, so they will have used the arrivals lounges there. I would also imagine some these guys & gals would have business in London or some other European capital & wouldn’t be solely coming to Ireland.
So again LHR etc would feature heavily in their itineraries, with a hop to DUB just being an add on.
Speaking for myself, I now only use EI as a feeder to get to LHR so that I can then use a “Real” airline for my onward travel. It’s only recently that I have been luckily enough to be able to travel in “J” on my travels & as such wouldn’t even dream of using EI to fly across the Atlantic. Even if they offer direct flights to my destination, such as JFK, BOS or ORD, preferring instead to travel with BA or VS.
Additionally, in most cases, certainly with BA anyway, I can advance book (albeit with restrictions) their “J” product & come out “Thousands of Euro” cheaper than EI’s vastly inferior “Premier” cabin. Or if not traveling in “J” I can use VS’s Premium Economy or BA’s World Traveler Plus, a cabin choice not available on EI’s service out of Ireland. Or for that matter any other airline crossing the Atlantic direct out of Ireland.
It’s worth noting though that if someone is looking for a “Cheap & Cheerful” (or not so cheerful most of the time) flight to the US, then EI’s economy product is just fine.
So I suspect taking all the above into account, I doubt if we’ll ever see the types of lounges found in LHR etc, in DUB. ORK or SNN.