I don't think you could utilise the 5th 320 to be honest. If only they had more flexibility with regard to crewing you could do some interesting things like W route the Gatwick and continue the Geneva year round.....for example. The routes that are performing badly out of Gatwick could be supported from Cork, i.e. maintain the destination slots and come from Cork instead, every other day.
I have to say, it was great to see 2 shamrocks on stand in Zurich side by side, the Dublin and Gatwick. It would have been nice if one was going to Cork....