Give Borini a chance! We all seen what a fresh Quagliarella did vs Slovakia at 2010 WC. Why take him along and not give him a chance?
On the other hand, Gio and Di Natale up front wouldn't work as they are 2 short strikers, Gio would be better at trequartista role.
Balotelli must start, as he would offer a bit of an aerial threat against Ireland's tall centre backs, and he's dying to score a goal after his misses in 2 previous games. Cassano seems to be tired and should perhaps be considered as a 2nd half sub, but keep Balo on!
This is how I'd start vs Ireland:
---------------Buffon---------------
Abate---Bonucci---Barzagli---Chiellini
------------------------------------
----De Rossi----Pirlo----Marchisio----
------------------------------------
--------------Giovinco--------------
-----------------------------------
-------Balotelli-------Di Natale------