Admittedly, there is now a lot of Irish narrow gauge in kit form from Worsley, that said, however, this is one of those chicken and egg situations, I know 00n3 modellers who have splashed out on a new Hornby TT120 scale 08 chassis the biggest draw back to the size/scale is the lack of a commercial locomotive chassis.
There are two items of narrow gauge which I think would work for most people, they are 1. the West Clare bogie Diesel or 2. the West Clare/Donegal Railcar, there is of course one outstanding NG loco and wagon set that you could put on a modern day layout and that would be a Wagonmaster and a train of Peat wagons, it could even be done as a complete roundy roundy layout with a loco and say 3 peat wagons. Then later on you could introduce a railcar. Would that work? I don't know, but I would have one if it was made.