1. See the
Sea Jet thread 
2.
Wouldn't another Ocean be more useful?
A larger version of
Ocean, that can carry and operate V/STOL aircraft (ie JSF) has been suggested in some quarters as an alternnative CVF.
3.
Seriously though, apart from fleet air defence I can't really think of anything CVF could achieve that a Cruise lobbing sub or Ocean couldn't.
Close Air Support for troops ashore? Organic Maritime Patrol? Organic AEW/ASACS?
4.
I dont think they're as vital as they used to be....
Surely littoral operations make them more vital?