I'm thinking you could swap a vertical tail between a Sea Harrier FRS.1 and an AV-8A to do the basic FV-8C and then do that again and do the aerodynamic and system upgrades for a FV-8C+, possibly also with a cockpit with screens instead of gages, much like the final F-20 cockpit (first couple F-20s had basically a F-5E cockpit, display-wise).
Glass cockpit would have come with radar replacement for the FV-8C+ a.k.a. Harrier 2001 programme
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The Vanguard Cruiser can very much be considered a forerunner of the Strike Cruisers that have become the backbone of Frontier Navy's aircraft carrier fleet. This warship class was meant for naval actions specifically against the League of Kings and their patron navies (at a time when the warlord alliance's high seas warfare capability was deemed to be limited to commerce raiding) so as to free the valuable and more expensive supercarriers for pursuing the Sages, a mysterious and presumably still-hostile entity that the Armies of Frontier Nations was founded to combat. As such, it's designed to be cheaper and to possess a degree of commonality with warships already in Frontier Navy service- as it turns out, AEGIS combat system ships.
Frontier Navy did not like its small airwing capacity (six Harrier FA.9As and six Merlin helicopters being specified as the typical composition in the design) to begin with, and two out of the six originally ordered ended up being cancelled when the Strike Cruiser programme was initiated, but the four that do serve would provide experience that benefited the Strike Cruiser programme tremendously. Nowadays they still find much employment as helicopter carriers supporting mine countermeasure and amphibious warfares.
Its armament initially consisted of a 5 inch gun, a 32-cell Mk.41 VLS, two quad AGM-84 Harpoon missile launchers, and three Phalanx CIWSs. A mid-life update saw provision for Naval Strike Missiles and replacement of Phalanx guns with 35mm Millennium cannons. The mast was replaced with an enclosed type for the existing SPS-40 air search and the newly-installed SEAPAR CIWS fire control radars. Cooperative Engagement Capability receiver-transmitter hardwares and Seamaster 100 surface search radar were also installed onto the enclosed mast.