My understanding is that you cannot add a new IR(R) to a JAR/EASA licence. You can add an IMC Rating to a National Licence and you can then get an EASA Licence issued with an IR(R) in it on the basis of your National Licence containing an IMC Rating. Similarly, if your JAR licence already contains an IMC Rating, it will become an IR(R) on conversion to an EASA licence.