I think that the IMCr as it stands answers what the majority of 'spam can' GA pilots want, which is the ability to climb on top of cloud, get somewhere and make an approach safely if required. Being excluded from airways and class A is probably not a big deal and I suspect there are very few IMCr holders who would plan a flight wholly in IMC conditions as it is basically unpleasant and not really what a private pilot is indulging in their hobby for.
I know this doesn't suit the even smaller group of GA, private pilots that fly more fancy equipment at higher levels and over further distances, but it is probably reasonable that if you want to mix it with the 'big boys' then you have to accept that the airspace your playing with is fundamentally their train set, so you play by 'their' rules.
An EIR appears to me to be useless... The important bit is not getting up there, or staying up there, it is getting down in one piece! An approach IR would seem to make more sense in that case.
My IMCr has saved my bacon once and I know others who wouldn't have got themselves in such a pickle for the sake of 15 hours training, so any replacement should be as accessible as it is currently. Currency is definitely key and perhaps this needs to be tightened up a little for the purposes of establishing a rating that can be used more widely.