Lude,
Most european HEMS services operate from Civilian airports so I'd imagine two at shannon, two in dublin and two in cork. With the GASU operating from Dublin, and Coastguard operating from Dublin and Galway.
As for the most realisable its all quite realisable, the most far out idea is the configuration of the helicopter fleet which in the framework of the civil aviation servcies and outsourced training is quite workable.
Samurai,
First of all from this and other posts I think you misunderstand the nature of the coastguard service in Ireland, our coastguard is essentially a rescue service and is completely civilian, the aviation support for the Coastguard is provided by a private company.
So the coastguard has nothing to do with the Air Corps or its budget, while the need for that many SAR helicopters should be apparent by our geography, and the need to avoid future disasters like the Egyptair crash.
Also the fact that some of the IAC Medium lifts will be using a search radar in the Maritime patrol and surveillance roles means that there will be a need for a back up service.
The CN-235 is listed for the Maritime patrol role only, the C-295 can carry 78 fully equipped troops and is a damn sight cheaper than similar sized alternatives.
You may have a point on the twin engined trainer role, and you're not the only one to raise it but I'd rather keep advanced training within the aircorps, so if anyone can suggest a smaller more suitable airframe to replace teh King air.....(Hmmm I wonder would a Bronco do?)