A couple of other options
- Push the 1715 back 10 minutes and make it express to Maynooth. This would make it attractive as a Longford service
- Extend the 1805 to Sligo
The real problem is that whatever is done has to be slotted in immediately ahead of a Maynooth service so as not to get caught behind.
The crazy thing about the timetable is that there are trains to Sligo at 1505, 1600 and 1705 when the real rush is after 1700. I've never understood the need for the 1600 to Sligo - would it not make a bit more sense to run it to Longford and have the 1805 go all the way?