No doubt it would come at the expense of Cork, with the Gastwick based aircraft flying to Shannon instead of Cork
During the summer there is 3 based A320 in LGW. (2 during winter)
A/C 1 - LGW - DUB
A/C 2 - LGW - AGP
A/C 3 - LGW - ORK & NOC
If A/C 1 can do DUB 5 times a day then A/C 3 can do SNN aswell.
or
If EI based a second A320 in SNN it could operate LGW and CDG.