The obvious solution to the paradox of overcrowding and low revenue is to limit the FTP scheme to off-peak travel. In practice this would identify a limited number of trains ineligible for FTP. There used to be a limitation of this sort on Dublin Bus, but the late Seamus Brennan was regarded as some sort of hero when he got rid of it.
With a minority Government and a useless minister for transport I can't see any such move happening (cue outrage and wailing on Joe Duffy). There is also the little problem of enforcement, and given the slack culture of revenue protection on Irish Rail that is a very real problem.