You'll find many FAA IR holders had IMC's beforehand.
And that's the rub - These people have gone through the proocess of getting the IR, and getting the aircraft that is capable so they can fly SAFE IFR throughout Europe, rather than the restrictions (UK IFR only, non-airways) that the IMC would give them.
What you're talking to many people would be a retrograde step.
Dublin - no 'N' reg means no exercise of FAA IR privileges - it would be JAA only