Finningley Boy,
Not a history lesson (plenty of good books out there) just pointing out your apples and oranges comparison.
Why would CAS be influencing frigates or destroyers? He doesn't operate any and never will. The RN/RM operates on the land, on the sea, under the sea and in the air so 1SL has an absolute requirement to ensure he influences what happens with aircraft that flew from his decks.
Given the binary SDSR requirement of either GR4 or Harrier you would not have found me arguing for the complete deletion of GR4. But that would have been an objective capability based position as opposed to those who might have other motives.
By SDSR the mass of Harrier had been whittled down well below that required of Defence so in order to achieve the most cost effective, most flexible, most deployable acceptable minimum mass of Offensive Support Defence should have gone for a GR4/GR9 mix until Typhoon (or JCA) provided what one or both could now.