There should be an imputed rent. And if you don't collect it, then you pay for the nursing home yourselves.
In your particular case, it may make sense to sell the house.
This is a big part of the problem, it rarely makes sense to sell the house, so they remain empty.
The house is assessed at 7.5% annually for 3 years only, so the maximum that can be taken is 22.5%, even if the person in care lives for 10 years or more. By keeping the house, at some stage the beneficiaries are going to get at least 77.5% of the house value.
If the house was sold at the time of entering nursing home care, one would be assessed on the proceeds indefinitely. The longer the person in care lived the less there would be in the pot.
Perhaps an incentive to sell when the person enters nursing home care rather than when they die which can be many years later would surely see many empty homes on the market. And / or would a substantial vacant property tax do the trick ?
When Fair Deal started it was 5% of property value capped at 15% and 5% of other assets.
By 2013 there were more people availing of Fair Deal and they were living longer so contributions were increased to 7.5% of property value capped at 22.5% and 7.5% of other assets.
Increasing the 7.5% again and extending the 3 year cap to 4 years would mean a lot more are paying themselves and at the same time leaving something for their beneficiaries.
I think these would be better solutions than the imputed rent solution which throws up numerous complications.