Take a look at the major European capitals on FR map, you'll find that no Irish destinations outside of DUB is served other than KIR-HHN. Even ORK is left with bucket and spade routes and the continent left to EI.
There has to be an opportunity to serve several of these from a second Irish airport. SNN is in the dog house, ORK too on charges, especially european routes where charges are higher and subsidies fewer.
So low-cost base like NOC can work for FR as it's proving on Spanish routes. In many ways it's the typical secondary airport FR pick all the time on the continent. People are willing to travel for cost and convenience of a smaller airport if it offers direct routes to their destination.
I may be wrong but I hope FR are thinking this way, it would also aid their agenda regarding DAA charges also.