JN - this is the way that business over numberplates has been done since the 1950s. The reason that analysis of worth (if you will) of numberplates' heritage isn't given much in the way of weight is because the AHB worked out when attempting to ascertain which squadrons should survive in the post-Sandys era that 'worth' is based upon subjective judgement. They concluded that going with what you call 'arcane' seniority rules was imperfect, but probably the best way to go about things.
There is some free-play, since if you go by 'arcane calculation' 74 wouldn't have reformed on the Phantom. 39, which was dormant at the time, was ahead in the queue, and there was a case for 45 to drop the TWCU reserve plate and step up to being the F-4J squadron.
3 suffered over 100% loss of unit establishment at Cambrai (pressed into service as mud-movers). 11 is arguably the first dedicated fighter squadron in any air force in the world (albeit the Vickers FB5 wasn't much of a fighter...). Until the Jag went, 6 had absolute unbroken service, which included flying around in Hurricane IIDs at skightly lower airspeed and height than was desirable in the face or the flak surrounding German armour. Who's to say that those squadrons don't have equally distinguished records of achievement/historical reasons for survival? Throw into the mix the risk of AOCs arbitrarily deciding that they didn't like X Squadron, bitter rivals of Y Squadron (the AOC's first squadron...), and the seniority-based approach looked sensible. Submit a well-reasoned piece of analysis to the AHB explaining why they should change this long-standing policy and I can guarantee that they'll at least consider it.
Leon - I suspect, by the by that the Air Staff probably has at least a small faction in it working out how to reform 74, since the records show that the period 1971-1984 was filled with efforts to reform the Tigers/Ginger Toms (delete according to prejudice) on Hunters, the Phantoms from 892, Victors (there was a hint of desperation creeping in here...) and then the aborted third Lightning squadron. I know that there's a suggestion out there that the squadron was deemed to have put up a 'black' by painting the tails of the Lightnings black when out in Singapore, which is why it took so long to reappear, but that simpy isn't the case, just as Trenchard's supposed 'revenge' against 8 Sqn becomes a difficult legend to sustain when you realise that he personally chose that numberplate to be one of the founding squadrons of the post-1918 RAF, and it ended up overseas because there was less chance of it being disbanded where it was than it it were in the UK... <removes anorak>