Is naval FJ a capability that we would want as a nation (Both Air Defence and Ground Attack / CAS)?
If YES - then this is in all likelihood best provided by the Navy as one of the weapons systems of the carrier platform.
I have read and posted elsewhere that there could be an effective split of capabilities across all three branches.
RN - Carrier borne FW - AD and GR/CAS - AEW if the carriers went CATOBAR
RW to support the Fleet - Lynx, Merlin, SK & SK AEW
RW to support 3 Cdo Brigade - Consider Merlin, Chinook and 'gunships'
in lieu of AH
Army - Tactical RW - Lynx, Puma, Merlin, Chinook, AH
Some Tactical FW - e.g Islander
RAF - Land based Air defence (for UK and projected forces) and ground
attack / strike / CAS (Wish I could say 'Bomber' and get a squadron or
two of BUFFs)
Strategic Recce / AWACS / ISTAR
All big ME assets
There is also a need to defend what you've got - so keep the Rocks for the RAF (and give them back Rapier?) - and there has never been a outpouring of complaints over the Nimrod MR - so leave that with the RAF too, rather than transferring them to the RN.
Naturally the RN FW will always be amphibious - so that allows a capability for forward deployment on short / rough fields when there is a restricted supply chain - Wasn't that the key reason that the Harrier went into KAF way before the Tonka.
The RAF could also keep Space Command and the Predator UAV for me.
Just my 2p's worth.