One thing I have not seen confirmed anywhere, which seems to me to be the crux of this matter is:-
According to IAA rules, is a ten-hour minimum rest period legal and/or considered safe?
If it is, then this is simply a straightforward industrial dispute.
If it is not, end of story. The company is trying to impose illegal conditions on its workforce.
CAA rules say it is not acceptable, but they don't apply in Ireland. IMHO, 10 hours is simply not safe. Pilots would be flying fatigued. I assume that the Irish equivalent of the ANO states that pilots should not fly if they know, or suspect that they are not fit?