I'm guessing that if there isn't a diesel engine under the floor, the floor can be closer to the platform level, so the wheelchair ramp can be less substantial.
Another factor that is important for wheelchair users to use the train without assistance - the location of the wheelchair ramps needs to be predictable (and preferably a wheelchair symbol painted in the right place on the platform). If the wheelchair doors are always the first and last doors, then there's no chance of them getting caught out if the train ends up the wrong way around (though if they don't have the range to get to Wexford, I'm not sure if that can happen).
However, if there's one toilet per 4-cars, will it be within reach of the wheelchair ramp doors?
Eventually, all trains should be accessible without assistance, but until they are there needs to be some way users can identify which services are from the timetable and website.