Well, there's the two-seat, radar-equipped Harrier II demonstrator I put together a decade ago for the Harrier SIG. I really need to revisit and upgrade that some time; I'd love to do that in 1/48 or 1/72 (got the pieces to do both if I can find them). Methinks that, combined with the extra hardpoints of the RAF version and the wingtip Sidewinders St. Louis trialed could make for an interesting basis for a very capable stretch version.
Too, I've got a copy of the small brochure for a FAA version of the AV-8B+; thinking of building it as a Harrier FGA.11 or FGR.11. I'm thinking that 804 Sqdn would be a user of these and would have one marked up for display and Tiger Meets.