Fuji
I do not agree that an experienced IR pilot goes rusty if not used for six months and becomes a danger.
IR flying is a bit like riding a bike or taking up skiing. When you first start the pilot will feel completely lost, very unatural and will struggle in hooking up all the elements of IR flying.
Then it clicks and becomes second nature. The pilot no longer even thinks about it and the process becomes as natural as flying VFR.
leave it six months and it will take maybe half an hour to get back in the groove. A bit like not skiing for 9 months to an experienced skier.
As he hits the slopes again it does not take long to get back into it.
The level of training and tolerances required for the IMCR no way approach the IR. It was designed as a get out of trouble minimal training rating.
If over time and experience the IMCR pilot builds his skills then yes it can be used as a mini IR.
Pace