The limitations of Dublin airport aside, I don't see any reason that they shouldn't be able to develop a transfer business.
They offer some of the best value transatlantic fares nowadays. Also, they are starting to develop a decent number of destinations out of Dublin, particularly in central and eastern Europe. Many of those destinations don't have direct transatlantic flights, so Dublin would be as good a transfer point as any considering the fares and that it wouldn't mean setting off in the wrong direction.
Of course, the website only allows you to book connections to a range of UK destinations, many of which have gained transatlantic access in recent years anyway...