Japan will not enter war without US airborne protection...UK and Italy are under NATO. Because of the fact that the the Brits are under NATO..the RN never thought they would need to operate without air cover and hence the Invincible class was conceived as a CAH. The Falkland war made them realize the limits of NATO coverage and suddenly they started putting jets on their carriers.
None of these are applicable to Pakistan...instead of outfitting one carrier for the ASW..why not have multiple frigates doing the same thing. At least because she will have more of them she can cover more area.
I assume by the statement 'being under NATO' you mean 'can rely on US carrier based air cover'. If not, then I have no idea what you mean.
It had nothing to do with NATO aircover. After all, the UK had its own fleet carriers in those days and wasn't dependent on US carriers for aircover beyond the reach of land based aviation. They were looking for something to lead and boost independent ASW groups (not the escort group of a carrier), which were employed to protect e.g. convoys crossing the atlantic with material for the reinforcements that would be flown in from te US and Canada after a Soviet assault on Europe (does the term 'Reforger' ring a bell?). Besides landing troops in support of Norway, such convoy protection was a major task of UK/RN in the NATO context. Any Harrier fighters put on board later were there to shoot down the occasional Soviet maritime patrol aircraft nosing around the ship and its escorts.
See e.g.
http://www.hazegray.org/navhist/carriers/uk_light.htm#inv-cl
http://www.hazegray.org/navhist/carriers/uk_helo.htm#herm
http://en.wikipedia.org/wiki/Invincible_class_aircraft_carrier
Both Hermes and the Invincible (class) predate the Falklands war. Both did already operate Harriers prior to that conflict, just in limited numbers (4-5 apiece).
Hermes converted from ASW carrier to VSTOL (Harrier) carrier in 1980. She refitted at Portsmouth 1980 to June 1981, during which time a 12-degree ski-jump and facilities for operating Sea Harriers were added. She embarked 800 sqn. with 8 Sea Harrier FRS1 Fighter and 826 sqn. with 9 Sea King HAS5 ASW.
Invincible commissioned in 1980, with Illustrious following mid 1982. Prior to 1982, R05Invincible's air group consisted purely of Sea King HAS.5 anti-submarine helicopters and Sea Harrier FRS.1 aircraft. Typically, 9 Sea Kings, and 4-5 Sea Harriers were embarked (nb. there are pics of the Hermes with exactly this a/c load just after her conversion to VSTOl carrier as well).
When the Falklands War broke out, Hermes was made the flagship of the British forces, setting sail for the South Atlantic just three days after the Argentine invasion of the Falkland Islands. She carried 12 BAe Sea Harrier FRS.Mk.1 jets of the Royal Navy's Fleet Air Arm, 10 Sea King as well as a troop of Special Air Service (SAS) and Royal Marines.
Invincible sailed together with Hermes into the Falklands conflict, under the command of Captain J.J. Black. She was joined by 9 Sea King helicopters of 820 Squadron and 8 Sea Harriers from 801 Squadron in the channel.
Mid-May these 20 Sea Harriers were reinforced by 8 more of No.809 NAS and 6 RAF GR.3's. A merchant vessel, the MV Atlantic Conveyor, became temporary home for these jets. No sooner did the Harriers GR3 transition to the HMS Hermes and the Sea Harriers to both Invincible and Hermes, and the MV Atlantic Conveyor was struck by an Argentine French-made Exocet missile, which caused an uncontrollable fire. After this burnt out, it was decided to sink her. An additional 4 GR3s reinforcments flew in directly to Hermes.
So, in all, 28 Sea Harriers and 10 Harrier GR3 were available for use by the Royal Navy with the Sea Harriers split between the HMS Invincible (12) and the HMS Hermes (16), which also got to carry all 10 Harrier GR3.
lIn the aftermath of the Falklands, the typical air group on the Invincible class became three AEW Sea Kings, nine ASW Sea Kings and eight or nine Sea Harriers.
As for Japan and Italy, if your argument is they c/would only field helicopter cruisers (CAH) and helicopter destroyers (DDH) because they are under land based JSDAF air cover or US naval air cover then you are essentially saying NONE of their ships should have been build because the argument of vulnerability to air attack would apply to ANY ship in those navies. So, IMHO, that's not a valid argument for not adopting helicopter carriers, helicopter cruisers, helicopter destroyers.