I'd agree that it is risky for Irish Rail to be looking at night services, but it is quite frankly ludicrous that the last train past Maynooth leaves Connolly at 1905. You can't even get to Kilcock after that.
If you went the intermodal route - i.e. make Irish Rail return tickets and passes acceptable on Bus Éireann, there would be hard data as to how much demand there was for later services. This would cost nothing to implement aside from the odd forgone bus fare from taxsaver ticket holders.
This would probably result in sufficient demand to justify more bus services which could even lead to a point where there were enough people on buses to justify a later train.