If I could go back in time? It would probably be the Hibernia, an unusual design even for the time and obviously significant in being the first loco in Ireland, then theres the Princess, the first loco built here
In terms of something that stood a realistic chance of survival I would agree about the Waterford and Tramore 2-2-2 tank, or indeed a main line 2-4-0 such as the WLWR G3 or MGWR G2, the latter of course not only being the last main line 2-4-0 in Ireland but Europe in general