Sousa my friend,
Once again you are putting out some great ideas, but if I may re-enter the fray by stepping back to basic requirments definition for what may be termed the Fixed Wing Utility Aircraft (FWUA).
These may be boiled down to: Reducing the expenditure of valuable blade time by performing non-tactical tasks currently allocated to helos with a less costly (across the board), commercially derived alternative. Specifically, but not all inclusive, tasks are: near all weather day/night admin transport of personnel and light cargo, transport of high value/senstive light cargo is this still a mission?), administrative light transport support to civil authorities such as national resources, forestry, agriculture, health, etc., which may include a benign visual surveillance/observation role.
Parachute training may be included, but I would not, as the need is not great and military parachute training cannot be adequately conducted with a utility aircraft type. If a new CN-235-300 or other appropriate airlifter is not procured, then make a deal with another air force, such as Sweden,to buy Hercules time, and/or lease the services of an appropriate civilan jump platform when required - Casa 212, Let-410, DC-3TP, etc.
Likewise for banner towing, a PC-9 job, and more advanced tactical surveillance operations - the purview of the Garda Islander and/or the 139's once the have their full FLIR fit.
I do not believe there is a requirement for the advanced STOL capability of an aircraft like the Quest Kodiak, though it is a superb aircraft and you are right to suggest it. Operating locations will be established airfields in Ireland, of which there are plenty, with possible occasional trips to the UK - not rough fields. Similarly, the DA 42, while a superb light twin training aircraft, is not a utility aircraft in terms of payload and range - carryng three pax and a few duffels does not satisfy the requirement.
The existing B200 is capable of perfomring many FWUA tasks, but is in need of an avionics update (which I understand is imminent) and will eventually run out of hours on the airfarme and have to retire. Until that happens there is no reason it cannot keep flying on task. I would even add Raisbeck enhancements if there is sufficent time left to justifty them.
That said, I believe a single Cessna Caravan remains the most practical solution, working in concert with the B200. A new Caravan goes for USD2.2+ million, but a used Caravan may be obtained on the market for as much as USD1.8 million for a low time 2006 model, down to an minimally acceptable USD1.3 million for a 2003(+/-) with higher time. In terms of the Kodiak, I have to echo Taj in that there are no guarantees of Quest viability as an aircraft manufacturing concern, and a production aircraft will certainly exceed the cost fo a new Caravan, based on economies of scale and a host of other factors, and a production Kodiak will not be available for three years at best.
My recommendation is a detailed study of the requirement vs. potential solutons, including keeping a number of the 172's on the roles for as long as they are useful. They are economical and paid for and easy to maintain and operate - barring the need for AVGAS.
Cheers,