DART+ (DART Expansion)

I obviously don't have numbers, but the AIRR looked into it and even they said it would be very expensive and not justifiable, for the AIRR:

The Review has considered interventions to enable faster and more frequent journeys between Rosslare Europort and
Dublin, including adding passing loops, tunnelling through Bray Head, developing a new railway along the M11 corridor, and building a new line for DART services along the N11 corridor. A more direct route between Cork and Waterford was also considered but found to be impractical due to the geography of this corridor.

Many of these solutions would be very costly and are unlikely to be justifiable as most railways in this region would not be
expected to support more than one or two trains per hour in each direction. It appears that the best way forward for
boosting connectivity in the South East of Ireland in the shorter term is to introduce an hourly shuttle service between
Wexford and Greystones, with DART services to be extended to Wicklow.

This is from the experts in this area and generally the people most positively predisposed to rail.

The reality is the ideas being proposed here simply aren't part of either the National Development Plan or the AIRR. While I won't say it will never happen, it certainly isn't going to happen in the next 30 years or so.