I don't think there can be a ban on temporary workers on non-French EU contracts working in France. Thus, crews could work for 11 months on Irish or BRK contracts, then be removed for 1 month, then return. Their basing is therefore temporary. N'est ce pas?
I think the french legislation doesn't even allow that. Otherwise easyJet, Cityjet, etc.. would have done it, no doubt.
As for NCE, there is no slots and it's very expensive!! all the slots are given to Air France.