Hess
As you are probably aware:
(i) All western air arms have substantially downsized since the Cold War and at the same time several of them have had to take on a lot more actual operational duties in the various areas of unrest in the Middle East and elsewhere. They are already stretched in meeting these demands. There would be major issues in Germany with them deploying combat assets abroad - this derives from history regarding that country's past military adventures!
(ii) The USAF has recently pulled out of Iceland. They were there as much for their own reasons as to protect Iceland. When US interests dictated that they did not need to remain, they left.
Therefore I think it very unlikely that another country would want to assume the task of providing Ireland with air defence. Furthermore, even if you envisage a country other than the US or UK doing this, I think there would still be strong opposition among the Irish population to stationing military combat assets of another country here. I think any such proposals would also need to be proofed against the Constitution and statute law, e.g. the Defence Act 1954, section 16 of which reads:
"16.—It shall be lawful for the Government to raise, train, equip, arm, pay and maintain defence forces to be called and known as Óglaigh na hÉireann or (in English) the Defence Forces."