I think the ultimate goal should be Belfast-Cork electric but there are a hell of a lot of ducks to get in a row (increased electricity grid supply without Kyoto fines or the dreaded nuclear, do you use interconnector or PPT, what about Connolly if PPT, what about interfering with DART if interconnector, the usual track issues, how do you persuade Translink to pay their share, etc. etc. etc. etc.....) and I therefore think it's pretty unlikely.
There are a lot of low or fairly low hanging fruit which need plucking first. For instance:
- Portarlington and Limerick Junction trackwork
- Finishing Cork commuter
- Cross-line linkage (or breaking the An Lar strangle) - what if you could get off a train at Leixlip and catch a IE or County Council run shuttle bus to Adamstown or Hazelhatch to get to Kildare? Metro West will bring that to some extent but given line curvature the Leixlip stations have the advantage of about the same distance and fewer stops travelled.
- Navan-Clonsilla and Navan-Drogheda (yes, both)
- Dundalk/Dunleer
- Athlone-Mullingar and doubling/looping Mullingar-Maynooth
- Galway commuter and doubling/looping Portarlington-Galway
- Limerick commuter from all four directions - Ennis, Adare, Roscrea, Cahir and a new rail spur from Cratloe to Shannon
- Waterford commuter - maybe even to New Ross
- Build the northeast curve towards Portlaoise, open Borris-on-Ossory station and close Ballybrophy station.
and in general infrastructure:
- dealing with erosion on the Wicklow line,
- dealing with all bridges with a speed limit of 30mph or less
- finding ways of removing at-grade crossings by closing/regrading/AutoLC, starting with any LCs on National Primary and then National Secondary and forcing NRA and county councils to pay 50:50 if they don't already
- aggressively developing stations as commercial spaces. No more 1-storey stations (like the new Midleton line stations) but 3-4 storey each side with integrated footbridges, shops, offices, daycare etc.
- Sell off all city centre freight yards and get the HGVs out of urban centres - instead build them at ports like Foynes and Rosslare and Balbriggan or at intersections between lines and orbital roads like the M50 or the Limerick Ring Road.