The trick would be how to do this while preserving decent planning. We don't want Kilcock to be Maynooth in a few years and having to push out to Enfield necessarily because the local council allows developers go mad in exchange for development charges. That said, it might be a handy spot to put a DART maintenance/storage yard for the Maynooth line so that trains can be started from there.
The other issue is catchment - it would be important to survey the users of the existing facilities to find out how many Maynooth parkers have come in from places like Edenderry or Kinnegad. If that number is significant then Enfield is the better terminus, no toll for NTR from Edenderry people either.
IE already start some trains from Enfield as it is. It would mean extra cost but that would really be about electrification since one would like to see that stretch double tracked either way, since it gives scope for more Sligo/Longford/Mullingar services, not to mention Moate/Athlone
Here in greater Toronto, feeder buses would be using the M4 to pass people to Maynooth and once demand required extend the terminus out. For example, feeder coaches would be starting from Edenderry and Kinnegad (with P&R car parks) and calling at Enfield/Johnstown and Kilcock and transferring passengers at the station in Maynooth, all on one ticket. Some buses could terminate at Enfield and turn back if they were connecting to a suburban ex Enfield, e.g. 0643, 0716, 0800.
That's how you manage commuters where trains are soon to be loco+12 bilevels: lots of feed. Very complicated stuff for Irish transport planners of course
In the meantime, if the Maynooth car park is oversubscribed maybe it should be restricted to carpoolers, to maximise the passengers for the available spaces.