The article linked above highlights the German approach which has been to electrify roughly 200km of single line track per year for nearly 70 years. The obvious advantage of that approach is that they can keep knowledge and equipment in-house, and instead of breaking up the project team at the end of a project, they can simply move on to the next electrification project.
If we took a similar approach to electrifying the Dublin area, with perhaps a more modest goal of 50km per year.
If there was a commitment to electrify the Dublin Cork line after the Dublin area, that could be planned while Dublin electrification was taking place, and the same team could move on to the project. By retaining skills and equipment, and exectrifying at a consistent rate so that the team wouldn't have to go through expansion and reduction for different sized projects, there should be significant savings over a more piecemeal approach.
I believe there are plans for the 201s to be re-engined. Perhaps they could be converted to Diesel-Electric engines with pantographs for bi-mode running, or perhaps new bi-mode locomotives would have to be bought, but the Mk4s should be able to be retained. It might take 8-10 years to electrify all the way to Cork, but the diesel generator of the locomotive would need less and less use as it progressed.
Some bi-mode DEMUs could also be bought for lines that run part way on the Dublin Cork tracks, and when electrification reaches other cities, new EMU stock could be introduced and the bi-mode stock cascaded onto lines that were partly electrified.
Sadly I see little chance of there being anything planned beyond the Dublin area, but I can dream.