Most likely is a 6th rotation to Dublin. There used to be six a few years ago and with BA now flying Dublin-Heathrow, it's in Aer Lingus interests to encourage connections through Amsterdam (where they still have a monopoly).
Cork might support extra rotations on Monday, Friday and Sunday, but 3 a day would be too much to have all week.
Similarly, I can't see a market in Shannon with its long haul services and plentiful Heathrow flights.
Knock could be the interesting one as it doesn't have a proper hub connection, but I'd feel even an A319 would be too big.
So, Dublin unless it's split along the lines of 3 days for one airport and four for another.