It's not only about FCN. Everyone should be treated with due regards to his seniority, period.
The real tragedy here is not the housing for those guys/girls, it's the fact that they were allowed to remain in the left seat and undermine all their colleagues who are junior to them.
It doesn't really matter that they are already CN, as there are tons of FOs who could do the job just as well given the chance.
The only fair way to deal with ANY issues, is to respect the seniority order.
To our management: you'll never hear anyone complain that the seniority order was respected.