With regret (the line south of Girvan is a little known scenic gem) I do agree.Electrification and frequency upgrade to Girvan but closure south thereof would probably be a pragmatic solution. Buses (ideally electric) could operate between Girvan and Stranraer/Cairnryan integrated to the timetable. This would probably be better for everyone as an hourly bus would likely be feasible.
I suspect an hourly express bus Girvan - Stranraer would be quicker than the train too, and as you say, could also serve Cairnryan (and Loch Ryan port at the other end of the village).
The extant RailSail Ayr - Cairnryan service has been reduced to only one per day and passes Girvan station ( I can understand why Ayr is a more appealing interchange than Girvan currently with half hourly direct services to/from Glasgow).
