I half expected a winter southern hemisphere route but USA is their goldmine
I'm not sure anywhere in the Southern Hemisphere could work from Dublin.
Australia and New Zealand are too far. There are very few European carriers who go the whole way there now, even from much bigger markets.
I can't imagine any significant demand for South America and IAG would probably regard expansion at Madrid as the best way to serve it.
The only place that might work on paper is South Africa. However, there's a problem of which airport there. Fly to Johannesburg and you lose a lot of Cape Town (which is the largest source of demand) traffic, as it's as you may as well connect in Heathrow, Frankfurt or Schiphol and avoid the unpleasantness of OR Tambo altogether. Fly to Cape Town and there are very few connections possibilities, so you lose the large chunk of people who were looking to go elsewhere.