The GAA will allow it, if its in the national interest - they'd lose too much public goodwill if they resisted. Croke was used by Ireland while the Aviva was being built on the Lansdowne Road site.and then two of
McHale Park (Castlebar, which is all seater), Semple Stadium (Thurles 55,000 capacity, 36,000 seating), Gaelic Ground (Limerick 49,500 capacity, 35,000 seating), Páirc Uí Chaoimh (Cork 43,500 19,500 seating), Fitzgerald Stadium (Killarney 43,000 capacity, 9,000 seating)
forgive me if i'm wrong, but don't the GAA take a fairly dim view of football being played at GAA stadiums as well?
The bigger issue with the ones you've listed, is that they are all falling down. The Irish site outside of Dublin would be Limerick, and would have to be Thomond Park, rather than the bigger, but decrepit Limerick GAA, about half a mile away. thomond is new, with a very modern design, and excellent facilities. The main stands are very (red) Amex. It holds 27k with two open ends, and they have loads of space to add more at one end, and enouggh for a few thousand at the other.